UBUNTU-CVE-2025-21731: High severity ubuntu/linux-azure vulnerability

Q: What conditions are required to trigger the use-after-free?

An attacker needs local access with low privileges and must be able to race Network Block Device (NBD) operations. The triggering sequence involves temporarily holding an nbd_config reference, disconnecting the device, reconfiguring it to queue receive work, and then releasing the held reference.

Q: Which Ubuntu kernel packages are listed as affected?

The listed packages are ubuntu/linux, ubuntu/linux-fips, ubuntu/linux-azure, ubuntu/linux-aws-fips, ubuntu/linux-azure-fips, ubuntu/linux-gcp-fips, ubuntu/linux-gcp, and ubuntu/linux-oracle.

Q: What change prevents the vulnerable reconnect path?

The fix clears the NBD_RT_BOUND state during nbd_genl_disconnect(). This causes subsequent nbd_genl_reconfigure() calls to fail rather than queueing receive work after disconnect.

Published Feb 27, 2025

Updated

In the Linux kernel, the following vulnerability has been resolved: nbd: don't allow reconnect after disconnect Following process can cause nbdconfig UAF: 1) grab nbdconfig temporarily; 2) nbdgenldisconnect() flush all recvwork() and release the initial reference: nbdgenldisconnect nbddisconnectandput nbddisconnect flushworkqueue(nbd->recvworkq) if (testandclearbit(NBDRTHASCONFIGREF, ...)) nbdconfigput -> due to step 1), reference is still not zero 3) nbdgenlreconfigure() queue recvwork() again; nbdgenlreconfigure config = nbdgetconfigunlocked(nbd) if (!config) -> succeed if (!testbit(NBDRTBOUND, ...)) -> succeed nbdreconnectsocket queuework(nbd->recvworkq, &args->work) 4) step 1) release the reference; 5) Finially, recvwork() will trigger UAF: recvwork nbdconfigput(nbd) -> nbdconfig is freed atomicdec(&config->recvthreads) -> UAF Fix the problem by clearing NBDRTBOUND in nbdgenldisconnect(), so that nbdgenlreconfigure() will fail.

Affected Software

200 affected componentsFixes available

ubuntu/linux-azure*

ubuntu/linux-aws-hwe*

ubuntu/linux-azure*

ubuntu/linux-gcp*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-oracle*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-aws-5.4<5.4.0-1146.156~18.04.1

5.4.0-1146.156~18.04.1

ubuntu/linux-azure*

ubuntu/linux-azure-4.15*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-5.4<5.4.0-1151.158~18.04.1

5.4.0-1151.158~18.04.1

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-4.15*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gcp-5.4<5.4.0-1149.158~18.04.1

5.4.0-1149.158~18.04.1

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-5.4<5.4.0-216.236~18.04.1

5.4.0-216.236~18.04.1

ubuntu/linux-hwe-edge*

ubuntu/linux-ibm-5.4<5.4.0-1092.97~18.04.1

5.4.0-1092.97~18.04.1

ubuntu/linux-kvm*

ubuntu/linux-oem*

ubuntu/linux-oracle*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-oracle-5.4<5.4.0-1144.154~18.04.1

5.4.0-1144.154~18.04.1

ubuntu/linux-raspi-5.4<5.4.0-1129.142~18.04.1

5.4.0-1129.142~18.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.4.0-216.236

5.4.0-216.236

ubuntu/linux-aws<5.4.0-1146.156

5.4.0-1146.156

ubuntu/linux-aws-5.15<5.15.0-1084.91~20.04.1

5.15.0-1084.91~20.04.1

ubuntu/linux-azure<5.4.0-1151.158

5.4.0-1151.158

ubuntu/linux-azure-5.15<5.15.0-1089.98~20.04.1

5.15.0-1089.98~20.04.1

ubuntu/linux-bluefield<5.4.0-1105.112

5.4.0-1105.112

ubuntu/linux-gcp<5.4.0-1149.158

5.4.0-1149.158

ubuntu/linux-gcp-5.15<5.15.0-1083.92~20.04.1

5.15.0-1083.92~20.04.1

ubuntu/linux-ibm<5.4.0-1092.97

5.4.0-1092.97

ubuntu/linux-ibm-5.15<5.15.0-1076.79~20.04.1

5.15.0-1076.79~20.04.1

ubuntu/linux-intel-iotg-5.15<5.15.0-1079.85~20.04.1

5.15.0-1079.85~20.04.1

ubuntu/linux-kvm<5.4.0-1133.142

5.4.0-1133.142

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-140.150~20.04.1

5.15.0-140.150~20.04.1

ubuntu/linux-oracle<5.4.0-1144.154

5.4.0-1144.154

ubuntu/linux-oracle-5.15<5.15.0-1081.87~20.04.1

5.15.0-1081.87~20.04.1

ubuntu/linux-raspi<5.4.0-1129.142

5.4.0-1129.142

ubuntu/linux-riscv-5.15<5.15.0-1079.83~20.04.1

5.15.0-1079.83~20.04.1

ubuntu/linux-xilinx-zynqmp<5.4.0-1064.68

5.4.0-1064.68

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.8*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

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<5.15.0-142.152~20.04.1

5.15.0-142.152~20.04.1

ubuntu/linux-hwe-5.8*

ubuntu/linux-intel-5.13*

ubuntu/linux-iot<5.4.0-1051.54

5.4.0-1051.54

ubuntu/linux-nvidia-tegra-5.15<5.15.0-1039.39~20.04.1

5.15.0-1039.39~20.04.1

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.8*

ubuntu/linux-aws-fips<5.4.0-1146.156+fips1

5.4.0-1146.156+fips1

ubuntu/linux-azure-fips<5.4.0-1151.158+fips1

5.4.0-1151.158+fips1

ubuntu/linux-fips<5.4.0-1120.130

5.4.0-1120.130

ubuntu/linux-gcp-fips<5.4.0-1149.158+fips1

5.4.0-1149.158+fips1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.15.0-140.150

5.15.0-140.150

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1084.91

5.15.0-1084.91

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1032.34~22.04.1

6.8.0-1032.34~22.04.1

ubuntu/linux-azure<5.15.0-1089.98

5.15.0-1089.98

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1034.39~22.04.1

6.8.0-1034.39~22.04.1

ubuntu/linux-azure-fde<5.15.0-1089.98.1

5.15.0-1089.98.1

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-gcp<5.15.0-1083.92

5.15.0-1083.92

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1033.35~22.04.1

6.8.0-1033.35~22.04.1

ubuntu/linux-gke<5.15.0-1081.87

5.15.0-1081.87

ubuntu/linux-gkeop<5.15.0-1066.74

5.15.0-1066.74

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-64.67~22.04.1

6.8.0-64.67~22.04.1

ubuntu/linux-ibm<5.15.0-1076.79

5.15.0-1076.79

ubuntu/linux-ibm-6.8<6.8.0-1029.29~22.04.1

6.8.0-1029.29~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1079.85

5.15.0-1079.85

ubuntu/linux-kvm<5.15.0-1080.85

5.15.0-1080.85

ubuntu/linux-lowlatency<5.15.0-140.150

5.15.0-140.150

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-64.67.1~22.04.1

6.8.0-64.67.1~22.04.1

ubuntu/linux-nvidia<5.15.0-1078.79

5.15.0-1078.79

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1031.34~22.04.1

6.8.0-1031.34~22.04.1

ubuntu/linux-nvidia-tegra<5.15.0-1037.37

5.15.0-1037.37

ubuntu/linux-nvidia-tegra-igx<5.15.0-1026.26

5.15.0-1026.26

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1081.87

5.15.0-1081.87

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1029.30~22.04.1

6.8.0-1029.30~22.04.1

ubuntu/linux-raspi<5.15.0-1078.81

5.15.0-1078.81

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-64.67~22.04.1

6.8.0-64.67~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp<5.15.0-1050.54

5.15.0-1050.54

ubuntu/linux-bluefield<5.15.0-1066.68

5.15.0-1066.68

ubuntu/linux-intel-iot-realtime<5.15.0-1077.79

5.15.0-1077.79

ubuntu/linux-realtime<5.15.0-1084.93

5.15.0-1084.93

ubuntu/linux-realtime-6.8<6.8.1-1025.26~22.04.1

6.8.1-1025.26~22.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1084.91+fips1

5.15.0-1084.91+fips1

ubuntu/linux-azure-fips<5.15.0-1089.98+fips1

5.15.0-1089.98+fips1

ubuntu/linux-fips<5.15.0-140.150+fips1

5.15.0-140.150+fips1

ubuntu/linux-gcp-fips<5.15.0-1083.92+fips1

5.15.0-1083.92+fips1

ubuntu/linux<6.8.0-64.67

6.8.0-64.67

ubuntu/linux-aws<6.8.0-1032.34

6.8.0-1032.34

ubuntu/linux-azure<6.8.0-1034.39

6.8.0-1034.39

ubuntu/linux-azure-6.11<6.11.0-1015.15~24.04.1

6.11.0-1015.15~24.04.1

ubuntu/linux-azure-nvidia<6.8.0-1022.23

6.8.0-1022.23

ubuntu/linux-gcp<6.8.0-1033.35

6.8.0-1033.35

ubuntu/linux-gcp-6.11<6.11.0-1015.15~24.04.1

6.11.0-1015.15~24.04.1

ubuntu/linux-gke<6.8.0-1028.32

6.8.0-1028.32

ubuntu/linux-gkeop<6.8.0-1015.17

6.8.0-1015.17

ubuntu/linux-hwe-6.11<6.11.0-26.26~24.04.1

6.11.0-26.26~24.04.1

ubuntu/linux-ibm<6.8.0-1029.29

6.8.0-1029.29

ubuntu/linux-lowlatency<6.8.0-64.67.1

6.8.0-64.67.1

ubuntu/linux-lowlatency-hwe-6.11<6.11.0-1014.15~24.04.1

6.11.0-1014.15~24.04.1

ubuntu/linux-nvidia<6.8.0-1031.34

6.8.0-1031.34

ubuntu/linux-nvidia-6.11<6.11.0-1010.10

6.11.0-1010.10

ubuntu/linux-nvidia-lowlatency<6.8.0-1031.34.1

6.8.0-1031.34.1

ubuntu/linux-nvidia-tegra<6.8.0-1008.8

6.8.0-1008.8

ubuntu/linux-oem-6.11<6.11.0-1022.22

6.11.0-1022.22

ubuntu/linux-oem-6.8<6.8.0-1031.31

6.8.0-1031.31

ubuntu/linux-oracle<6.8.0-1029.30

6.8.0-1029.30

ubuntu/linux-raspi<6.8.0-1031.35

6.8.0-1031.35

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-xilinx<6.8.0-1017.18

6.8.0-1017.18

ubuntu/linux-raspi-realtime<6.8.0-2026.27

6.8.0-2026.27

ubuntu/linux-realtime<6.8.1-1025.26

6.8.1-1025.26

ubuntu/linux-fips<6.8.0-78.78+fips1

6.8.0-78.78+fips1

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-aws-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1146.156~18.04.1
Upgrade
Upgrade ubuntu/linux-azure-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1151.158~18.04.1
Upgrade
Upgrade ubuntu/linux-gcp-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1149.158~18.04.1
Upgrade
Upgrade ubuntu/linux-hwe-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-216.236~18.04.1
Upgrade
Upgrade ubuntu/linux-ibm-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1092.97~18.04.1
Upgrade
Upgrade ubuntu/linux-oracle-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1144.154~18.04.1
Upgrade
Upgrade ubuntu/linux-raspi-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1129.142~18.04.1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 5.4.0-216.236
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 5.4.0-1146.156
Upgrade
Upgrade ubuntu/linux-aws-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1084.91~20.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 5.4.0-1151.158
Upgrade
Upgrade ubuntu/linux-azure-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1089.98~20.04.1
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 5.4.0-1105.112
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 5.4.0-1149.158
Upgrade
Upgrade ubuntu/linux-gcp-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1083.92~20.04.1
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 5.4.0-1092.97
Upgrade
Upgrade ubuntu/linux-ibm-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1076.79~20.04.1
Upgrade
Upgrade ubuntu/linux-intel-iotg-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1079.85~20.04.1
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 5.4.0-1133.142
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-140.150~20.04.1
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 5.4.0-1144.154
Upgrade
Upgrade ubuntu/linux-oracle-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1081.87~20.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 5.4.0-1129.142
Upgrade
Upgrade ubuntu/linux-riscv-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1079.83~20.04.1
Upgrade
Upgrade ubuntu/linux-xilinx-zynqmp to a version that resolves this vulnerability.
Fixed in 5.4.0-1064.68
Upgrade
Upgrade ubuntu/linux-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-142.152~20.04.1
Upgrade
Upgrade ubuntu/linux-iot to a version that resolves this vulnerability.
Fixed in 5.4.0-1051.54
Upgrade
Upgrade ubuntu/linux-nvidia-tegra-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1039.39~20.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1146.156+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1151.158+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1120.130
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1149.158+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 5.15.0-140.150
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 5.15.0-1084.91
Upgrade
Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1032.34~22.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 5.15.0-1089.98
Upgrade
Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1034.39~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 5.15.0-1089.98.1
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 5.15.0-1083.92
Upgrade
Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1033.35~22.04.1
Upgrade
Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 5.15.0-1081.87
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 5.15.0-1066.74
Upgrade
Upgrade ubuntu/linux-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-64.67~22.04.1
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 5.15.0-1076.79
Upgrade
Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.29~22.04.1
Upgrade
Upgrade ubuntu/linux-intel-iotg to a version that resolves this vulnerability.
Fixed in 5.15.0-1079.85
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 5.15.0-1080.85
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 5.15.0-140.150
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-64.67.1~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 5.15.0-1078.79
Upgrade
Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1031.34~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 5.15.0-1037.37
Upgrade
Upgrade ubuntu/linux-nvidia-tegra-igx to a version that resolves this vulnerability.
Fixed in 5.15.0-1026.26
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 5.15.0-1081.87
Upgrade
Upgrade ubuntu/linux-oracle-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.30~22.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 5.15.0-1078.81
Upgrade
Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-64.67~22.04.1
Upgrade
Upgrade ubuntu/linux-xilinx-zynqmp to a version that resolves this vulnerability.
Fixed in 5.15.0-1050.54
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 5.15.0-1066.68
Upgrade
Upgrade ubuntu/linux-intel-iot-realtime to a version that resolves this vulnerability.
Fixed in 5.15.0-1077.79
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 5.15.0-1084.93
Upgrade
Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1025.26~22.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1084.91+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1089.98+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-140.150+fips1
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1083.92+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-64.67
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.8.0-1032.34
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.8.0-1034.39
Upgrade
Upgrade ubuntu/linux-azure-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1015.15~24.04.1
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Upgrade ubuntu/linux-azure-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1022.23
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Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.8.0-1033.35
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Upgrade ubuntu/linux-gcp-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1015.15~24.04.1
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Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 6.8.0-1028.32
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Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 6.8.0-1015.17
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Upgrade ubuntu/linux-hwe-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-26.26~24.04.1
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Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.29
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Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-64.67.1
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Upgrade ubuntu/linux-lowlatency-hwe-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1014.15~24.04.1
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Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1031.34
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Upgrade ubuntu/linux-nvidia-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1010.10
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Fixed in 6.8.0-1031.34.1
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Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 6.8.0-1008.8
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Upgrade ubuntu/linux-oem-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1022.22
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Upgrade ubuntu/linux-oem-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1031.31
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Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.30
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Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.8.0-1031.35
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Upgrade ubuntu/linux-xilinx to a version that resolves this vulnerability.
Fixed in 6.8.0-1017.18
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Fixed in 6.8.0-2026.27
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Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.8.1-1025.26
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Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-78.78+fips1
Configuration
Clear the NBD_RT_BOUND bit in nbd_genl_disconnect() so that nbd_genl_reconfigure() fails and cannot queue recv_work() after disconnect.
Linux kernel NBD NBD_RT_BOUND = cleared

Event History

Feb 27, 2025

CVE Published

via OSV·02:15 AM

Data Sourced

via OSV·02:15 AM

DescriptionSeverityAffected Software

Frequently Asked Questions

What conditions are required to trigger the use-after-free?

An attacker needs local access with low privileges and must be able to race Network Block Device (NBD) operations. The triggering sequence involves temporarily holding an nbd_config reference, disconnecting the device, reconfiguring it to queue receive work, and then releasing the held reference.

Which Ubuntu kernel packages are listed as affected?

The listed packages are ubuntu/linux, ubuntu/linux-fips, ubuntu/linux-azure, ubuntu/linux-aws-fips, ubuntu/linux-azure-fips, ubuntu/linux-gcp-fips, ubuntu/linux-gcp, and ubuntu/linux-oracle.

What change prevents the vulnerable reconnect path?

The fix clears the NBD_RT_BOUND state during nbd_genl_disconnect(). This causes subsequent nbd_genl_reconfigure() calls to fail rather than queueing receive work after disconnect.

UBUNTU-CVE-2025-21731: High severity ubuntu/linux-azure vulnerability

Affected Software

Remediation

Event History

Frequently Asked Questions

What conditions are required to trigger the use-after-free?

Which Ubuntu kernel packages are listed as affected?

What change prevents the vulnerable reconnect path?

Company

Resources

Contact

Frequently Asked Questions

What conditions are required to trigger the use-after-free?

Which Ubuntu kernel packages are listed as affected?

What change prevents the vulnerable reconnect path?