UBUNTU-CVE-2026-23405: Medium severity ubuntu/linux vulnerability

Q: Who is realistically exposed to this issue?

Systems running an affected Ubuntu Linux kernel variant with AppArmor policy namespaces available are exposed. The listed packages include standard Ubuntu kernels and AWS, Azure, GCP, FIPS, AWS FIPS, and Azure FIPS kernel variants.

Q: What access does an attacker need to exploit it?

An attacker needs local access and low privileges. No user interaction is required.

Q: What is the practical impact of successful exploitation?

An attacker can create arbitrarily deep nested policy namespaces and exhaust system resources, resulting in a denial of service. The provided severity vector indicates no confidentiality or integrity impact.

Q: What configuration condition enables the issue?

The issue concerns AppArmor policy namespaces. Policy namespace nesting was not bounded independently of user namespace limits, because policy namespaces are not strictly tied to user namespaces.

Published Apr 1, 2026

Updated

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix: limit the number of levels of policy namespaces Currently the number of policy namespaces is not bounded relying on the user namespace limit. However policy namespaces aren't strictly tied to user namespaces and it is possible to create them and nest them arbitrarily deep which can be used to exhaust system resource. Hard cap policy namespaces to the same depth as user namespaces.

Affected Software

242 affected componentsFixes available

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-azure<4.15.0-1200.215~14.04.1

4.15.0-1200.215~14.04.1

ubuntu/linux-lts-xenial*

ubuntu/linux-aws-hwe<4.15.0-1191.204~16.04.1

4.15.0-1191.204~16.04.1

ubuntu/linux-azure<4.15.0-1200.215~16.04.1

4.15.0-1200.215~16.04.1

ubuntu/linux-gcp<4.15.0-1184.201~16.04.1

4.15.0-1184.201~16.04.1

ubuntu/linux-hwe<4.15.0-249.261~16.04.1

4.15.0-249.261~16.04.1

ubuntu/linux-oracle<4.15.0-1153.164~16.04.1

4.15.0-1153.164~16.04.1

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-hwe-edge*

ubuntu/linux-kvm*

ubuntu/linux-fips*

ubuntu/linux<4.15.0-249.261

4.15.0-249.261

ubuntu/linux-aws<4.15.0-1191.204

4.15.0-1191.204

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-aws-5.4<5.4.0-1156.166~18.04.1

5.4.0-1156.166~18.04.1

ubuntu/linux-azure*

ubuntu/linux-azure-4.15<4.15.0-1200.215

4.15.0-1200.215

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-5.4<5.4.0-1161.167~18.04.1

5.4.0-1161.167~18.04.1

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-4.15<4.15.0-1184.201

4.15.0-1184.201

ubuntu/linux-gcp-5.3*

ubuntu/linux-gcp-5.4<5.4.0-1159.168~18.04.1

5.4.0-1159.168~18.04.1

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-5.4<5.4.0-227.247~18.04.1

5.4.0-227.247~18.04.1

ubuntu/linux-hwe-edge*

ubuntu/linux-ibm-5.4<5.4.0-1102.107~18.04.1

5.4.0-1102.107~18.04.1

ubuntu/linux-kvm<4.15.0-1173.178

4.15.0-1173.178

ubuntu/linux-oem*

ubuntu/linux-oracle<4.15.0-1153.164

4.15.0-1153.164

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-oracle-5.4<5.4.0-1154.164~18.04.1

5.4.0-1154.164~18.04.1

ubuntu/linux-raspi-5.4<5.4.0-1139.152~18.04.1

5.4.0-1139.152~18.04.1

ubuntu/linux-aws-fips<4.15.0-2129.135

4.15.0-2129.135

ubuntu/linux-azure-fips<4.15.0-2109.115

4.15.0-2109.115

ubuntu/linux-fips<4.15.0-1146.158

4.15.0-1146.158

ubuntu/linux-gcp-fips<4.15.0-2092.98

4.15.0-2092.98

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.4.0-227.247

5.4.0-227.247

ubuntu/linux-aws<5.4.0-1156.166

5.4.0-1156.166

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.15<5.15.0-1103.110~20.04.1

5.15.0-1103.110~20.04.1

ubuntu/linux-aws-5.8*

ubuntu/linux-azure<5.4.0-1160.166

5.4.0-1160.166

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.15<5.15.0-1110.119~20.04.1

5.15.0-1110.119~20.04.1

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-bluefield<5.4.0-1116.123

5.4.0-1116.123

ubuntu/linux-gcp<5.4.0-1159.168

5.4.0-1159.168

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.15<5.15.0-1103.112~20.04.1

5.15.0-1103.112~20.04.1

ubuntu/linux-gcp-5.8*

ubuntu/linux-gke*

ubuntu/linux-gke-5.15*

ubuntu/linux-gkeop*

ubuntu/linux-gkeop-5.15*

ubuntu/linux-hwe-5.11*

ubuntu/linux-hwe-5.13*

ubuntu/linux-hwe-5.15<5.15.0-173.183~20.04.1

5.15.0-173.183~20.04.1

ubuntu/linux-hwe-5.8*

ubuntu/linux-ibm<5.4.0-1102.107

5.4.0-1102.107

ubuntu/linux-ibm-5.15<5.15.0-1097.100~20.04.1

5.15.0-1097.100~20.04.1

ubuntu/linux-intel-5.13*

ubuntu/linux-intel-iotg-5.15<5.15.0-1098.104~20.04.1

5.15.0-1098.104~20.04.1

ubuntu/linux-iot<5.4.0-1060.63

5.4.0-1060.63

ubuntu/linux-kvm<5.4.0-1143.152

5.4.0-1143.152

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-173.183~20.04.1

5.15.0-173.183~20.04.1

ubuntu/linux-nvidia-tegra-5.15<5.15.0-1055.55~20.04.1

5.15.0-1055.55~20.04.1

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle<5.4.0-1154.164

5.4.0-1154.164

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.15<5.15.0-1100.106~20.04.1

5.15.0-1100.106~20.04.1

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi<5.4.0-1139.152

5.4.0-1139.152

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.15<5.15.0-1098.102~20.04.1

5.15.0-1098.102~20.04.1

ubuntu/linux-riscv-5.8*

ubuntu/linux-xilinx-zynqmp<5.4.0-1074.78

5.4.0-1074.78

ubuntu/linux-aws-fips<5.4.0-1156.166+fips1

5.4.0-1156.166+fips1

ubuntu/linux-azure-fips<5.4.0-1160.166+fips1

5.4.0-1160.166+fips1

ubuntu/linux-fips<5.4.0-1130.140

5.4.0-1130.140

ubuntu/linux-gcp-fips<5.4.0-1159.168+fips1

5.4.0-1159.168+fips1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.15.0-173.183

5.15.0-173.183

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1103.110

5.15.0-1103.110

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1050.53~22.04.1

6.8.0-1050.53~22.04.1

ubuntu/linux-azure<5.15.0-1109.118

5.15.0-1109.118

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1051.57~22.04.1

6.8.0-1051.57~22.04.1

ubuntu/linux-azure-fde<5.15.0-1109.118.1

5.15.0-1109.118.1

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8<6.8.0-1058.65~22.04.1

6.8.0-1058.65~22.04.1

ubuntu/linux-gcp<5.15.0-1103.112

5.15.0-1103.112

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1052.55~22.04.1

6.8.0-1052.55~22.04.1

ubuntu/linux-gke<5.15.0-1099.105

5.15.0-1099.105

ubuntu/linux-gkeop<5.15.0-1086.94

5.15.0-1086.94

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-106.106~22.04.1

6.8.0-106.106~22.04.1

ubuntu/linux-ibm<5.15.0-1097.100

5.15.0-1097.100

ubuntu/linux-ibm-6.8<6.8.0-1049.49~22.04.1

6.8.0-1049.49~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1098.104

5.15.0-1098.104

ubuntu/linux-kvm<5.15.0-1095.100

5.15.0-1095.100

ubuntu/linux-lowlatency<5.15.0-173.183

5.15.0-173.183

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-106.106.1~22.04.1

6.8.0-106.106.1~22.04.1

ubuntu/linux-nvidia<5.15.0-1098.99

5.15.0-1098.99

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1049.52~22.04.1

6.8.0-1049.52~22.04.1

ubuntu/linux-nvidia-tegra<5.15.0-1055.55

5.15.0-1055.55

ubuntu/linux-nvidia-tegra-igx<5.15.0-1044.44

5.15.0-1044.44

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1100.106

5.15.0-1100.106

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1047.48~22.04.1

6.8.0-1047.48~22.04.1

ubuntu/linux-raspi<5.15.0-1097.100

5.15.0-1097.100

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-106.106~22.04.1

6.8.0-106.106~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp<5.15.0-1067.71

5.15.0-1067.71

ubuntu/linux-bluefield<5.15.0-1087.89

5.15.0-1087.89

ubuntu/linux-intel-iot-realtime<5.15.0-1096.98

5.15.0-1096.98

ubuntu/linux-realtime<5.15.0-1102.111

5.15.0-1102.111

ubuntu/linux-realtime-6.8<6.8.1-1045.46~22.04.1

6.8.1-1045.46~22.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1103.110+fips1

5.15.0-1103.110+fips1

ubuntu/linux-azure-fips<5.15.0-1109.118+fips1

5.15.0-1109.118+fips1

ubuntu/linux-fips<5.15.0-173.183+fips1

5.15.0-173.183+fips1

ubuntu/linux-gcp-fips<5.15.0-1103.112+fips1

5.15.0-1103.112+fips1

ubuntu/linux<6.8.0-106.106

6.8.0-106.106

ubuntu/linux-aws<6.8.0-1050.53

6.8.0-1050.53

ubuntu/linux-aws-6.14*

ubuntu/linux-aws-6.17<6.17.0-1009.9~24.04.2

6.17.0-1009.9~24.04.2

ubuntu/linux-azure<6.8.0-1051.57

6.8.0-1051.57

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-6.17<6.17.0-1010.10~24.04.1

6.17.0-1010.10~24.04.1

ubuntu/linux-azure-fde<6.8.0-1058.65

6.8.0-1058.65

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-nvidia<6.8.0-1039.42

6.8.0-1039.42

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1052.55

6.8.0-1052.55

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gcp-6.17<6.17.0-1009.9~24.04.3

6.17.0-1009.9~24.04.3

ubuntu/linux-gke<6.8.0-1048.53

6.8.0-1048.53

ubuntu/linux-gkeop<6.8.0-1035.38

6.8.0-1035.38

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-hwe-6.17<6.17.0-19.19~24.04.2

6.17.0-19.19~24.04.2

ubuntu/linux-ibm<6.8.0-1049.49

6.8.0-1049.49

ubuntu/linux-lowlatency<6.8.0-106.106.1

6.8.0-106.106.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1049.52

6.8.0-1049.52

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17<6.17.0-1014.14

6.17.0-1014.14

ubuntu/linux-nvidia-lowlatency<6.8.0-1049.52.1

6.8.0-1049.52.1

ubuntu/linux-nvidia-tegra<6.8.0-1020.20

6.8.0-1020.20

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17<6.17.0-1017.17

6.17.0-1017.17

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1047.48

6.8.0-1047.48

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17<6.17.0-1009.9~24.04.1

6.17.0-1009.9~24.04.1

ubuntu/linux-raspi<6.8.0-1050.54

6.8.0-1050.54

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-riscv-6.17<6.17.0-19.19.1~24.04.1

6.17.0-19.19.1~24.04.1

ubuntu/linux-xilinx<6.8.0-1028.29

6.8.0-1028.29

ubuntu/linux-bluefield<6.8.0-1017.21

6.8.0-1017.21

ubuntu/linux-raspi-realtime<6.8.0-2040.41

6.8.0-2040.41

ubuntu/linux-realtime<6.8.1-1045.46

6.8.1-1045.46

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17<6.17.0-1008.9~24.04.1

6.17.0-1008.9~24.04.1

ubuntu/linux-aws-fips<6.8.0-1050.53+fips1

6.8.0-1050.53+fips1

ubuntu/linux-azure-fips<6.8.0-1052.58+fips1

6.8.0-1052.58+fips1

ubuntu/linux-fips<6.8.0-106.106+fips1

6.8.0-106.106+fips1

ubuntu/linux-gcp-fips<6.8.0-1052.55+fips1

6.8.0-1052.55+fips1

ubuntu/linux<6.17.0-19.19

6.17.0-19.19

ubuntu/linux-aws<6.17.0-1009.9

6.17.0-1009.9

ubuntu/linux-azure<6.17.0-1010.10

6.17.0-1010.10

ubuntu/linux-azure-fde*

ubuntu/linux-gcp<6.17.0-1009.9

6.17.0-1009.9

ubuntu/linux-oracle<6.17.0-1009.9

6.17.0-1009.9

ubuntu/linux-raspi<6.17.0-1010.10

6.17.0-1010.10

ubuntu/linux-realtime<6.17.0-1008.9

6.17.0-1008.9

ubuntu/linux-riscv<6.17.0-19.19.1

6.17.0-19.19.1

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 4.15.0-1200.215~14.04.1
Upgrade
Upgrade ubuntu/linux-aws-hwe to a version that resolves this vulnerability.
Fixed in 4.15.0-1191.204~16.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 4.15.0-1200.215~16.04.1
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 4.15.0-1184.201~16.04.1
Upgrade
Upgrade ubuntu/linux-hwe to a version that resolves this vulnerability.
Fixed in 4.15.0-249.261~16.04.1
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 4.15.0-1153.164~16.04.1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 4.15.0-249.261
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 4.15.0-1191.204
Upgrade
Upgrade ubuntu/linux-aws-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1156.166~18.04.1
Upgrade
Upgrade ubuntu/linux-azure-4.15 to a version that resolves this vulnerability.
Fixed in 4.15.0-1200.215
Upgrade
Upgrade ubuntu/linux-azure-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1161.167~18.04.1
Upgrade
Upgrade ubuntu/linux-gcp-4.15 to a version that resolves this vulnerability.
Fixed in 4.15.0-1184.201
Upgrade
Upgrade ubuntu/linux-gcp-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1159.168~18.04.1
Upgrade
Upgrade ubuntu/linux-hwe-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-227.247~18.04.1
Upgrade
Upgrade ubuntu/linux-ibm-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1102.107~18.04.1
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 4.15.0-1173.178
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 4.15.0-1153.164
Upgrade
Upgrade ubuntu/linux-oracle-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1154.164~18.04.1
Upgrade
Upgrade ubuntu/linux-raspi-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1139.152~18.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 4.15.0-2129.135
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 4.15.0-2109.115
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 4.15.0-1146.158
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 4.15.0-2092.98
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 5.4.0-227.247
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 5.4.0-1156.166
Upgrade
Upgrade ubuntu/linux-aws-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1103.110~20.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 5.4.0-1160.166
Upgrade
Upgrade ubuntu/linux-azure-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1110.119~20.04.1
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 5.4.0-1116.123
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 5.4.0-1159.168
Upgrade
Upgrade ubuntu/linux-gcp-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1103.112~20.04.1
Upgrade
Upgrade ubuntu/linux-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-173.183~20.04.1
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 5.4.0-1102.107
Upgrade
Upgrade ubuntu/linux-ibm-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1097.100~20.04.1
Upgrade
Upgrade ubuntu/linux-intel-iotg-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1098.104~20.04.1
Upgrade
Upgrade ubuntu/linux-iot to a version that resolves this vulnerability.
Fixed in 5.4.0-1060.63
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 5.4.0-1143.152
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-173.183~20.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1055.55~20.04.1
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 5.4.0-1154.164
Upgrade
Upgrade ubuntu/linux-oracle-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1100.106~20.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 5.4.0-1139.152
Upgrade
Upgrade ubuntu/linux-riscv-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1098.102~20.04.1
Upgrade
Upgrade ubuntu/linux-xilinx-zynqmp to a version that resolves this vulnerability.
Fixed in 5.4.0-1074.78
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1156.166+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1160.166+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1130.140
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1159.168+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 5.15.0-173.183
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 5.15.0-1103.110
Upgrade
Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.53~22.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 5.15.0-1109.118
Upgrade
Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1051.57~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 5.15.0-1109.118.1
Upgrade
Upgrade ubuntu/linux-azure-fde-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.65~22.04.1
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 5.15.0-1103.112
Upgrade
Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.55~22.04.1
Upgrade
Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 5.15.0-1099.105
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 5.15.0-1086.94
Upgrade
Upgrade ubuntu/linux-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106~22.04.1
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 5.15.0-1097.100
Upgrade
Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.49~22.04.1
Upgrade
Upgrade ubuntu/linux-intel-iotg to a version that resolves this vulnerability.
Fixed in 5.15.0-1098.104
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 5.15.0-1095.100
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 5.15.0-173.183
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106.1~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 5.15.0-1098.99
Upgrade
Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.52~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 5.15.0-1055.55
Upgrade
Upgrade ubuntu/linux-nvidia-tegra-igx to a version that resolves this vulnerability.
Fixed in 5.15.0-1044.44
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 5.15.0-1100.106
Upgrade
Upgrade ubuntu/linux-oracle-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1047.48~22.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 5.15.0-1097.100
Upgrade
Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106~22.04.1
Upgrade
Upgrade ubuntu/linux-xilinx-zynqmp to a version that resolves this vulnerability.
Fixed in 5.15.0-1067.71
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 5.15.0-1087.89
Upgrade
Upgrade ubuntu/linux-intel-iot-realtime to a version that resolves this vulnerability.
Fixed in 5.15.0-1096.98
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 5.15.0-1102.111
Upgrade
Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1045.46~22.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1103.110+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1109.118+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-173.183+fips1
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1103.112+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.53
Upgrade
Upgrade ubuntu/linux-aws-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1009.9~24.04.2
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.8.0-1051.57
Upgrade
Upgrade ubuntu/linux-azure-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1010.10~24.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.65
Upgrade
Upgrade ubuntu/linux-azure-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1039.42
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.55
Upgrade
Upgrade ubuntu/linux-gcp-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1009.9~24.04.3
Upgrade
Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 6.8.0-1048.53
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 6.8.0-1035.38
Upgrade
Upgrade ubuntu/linux-hwe-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-19.19~24.04.2
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.49
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.52
Upgrade
Upgrade ubuntu/linux-nvidia-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1014.14
Upgrade
Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.52.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 6.8.0-1020.20
Upgrade
Upgrade ubuntu/linux-oem-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1017.17
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.8.0-1047.48
Upgrade
Upgrade ubuntu/linux-oracle-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1009.9~24.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.54
Upgrade
Upgrade ubuntu/linux-riscv-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-19.19.1~24.04.1
Upgrade
Upgrade ubuntu/linux-xilinx to a version that resolves this vulnerability.
Fixed in 6.8.0-1028.29
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 6.8.0-1017.21
Upgrade
Upgrade ubuntu/linux-raspi-realtime to a version that resolves this vulnerability.
Fixed in 6.8.0-2040.41
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.8.1-1045.46
Upgrade
Upgrade ubuntu/linux-realtime-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.9~24.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.53+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.58+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106+fips1
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.55+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.17.0-19.19
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.17.0-1009.9
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.17.0-1010.10
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.17.0-1009.9
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.17.0-1009.9
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.17.0-1010.10
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.9
Upgrade
Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.
Fixed in 6.17.0-19.19.1
Compensating control
Hard-cap AppArmor policy namespace nesting to the same depth limit as user namespaces to prevent arbitrarily deep policy namespace creation from exhausting system resources.

Event History

Apr 1, 2026

CVE Published

via OSV·09:16 AM

Data Sourced

via OSV·09:16 AM

DescriptionSeverityAffected Software

Frequently Asked Questions

Who is realistically exposed to this issue?

Systems running an affected Ubuntu Linux kernel variant with AppArmor policy namespaces available are exposed. The listed packages include standard Ubuntu kernels and AWS, Azure, GCP, FIPS, AWS FIPS, and Azure FIPS kernel variants.

What access does an attacker need to exploit it?

An attacker needs local access and low privileges. No user interaction is required.

What is the practical impact of successful exploitation?

An attacker can create arbitrarily deep nested policy namespaces and exhaust system resources, resulting in a denial of service. The provided severity vector indicates no confidentiality or integrity impact.

What configuration condition enables the issue?

The issue concerns AppArmor policy namespaces. Policy namespace nesting was not bounded independently of user namespace limits, because policy namespaces are not strictly tied to user namespaces.

UBUNTU-CVE-2026-23405: Medium severity ubuntu/linux vulnerability

Affected Software

Remediation

Event History

Frequently Asked Questions

Who is realistically exposed to this issue?

What access does an attacker need to exploit it?

What is the practical impact of successful exploitation?

What configuration condition enables the issue?

Company

Resources

Contact

Frequently Asked Questions

Who is realistically exposed to this issue?

What access does an attacker need to exploit it?

What is the practical impact of successful exploitation?

What configuration condition enables the issue?