UBUNTU-CVE-2026-31669: Use After Free

Q: Which systems are exposed to this issue?

The issue affects the listed Ubuntu Linux kernel packages when MPTCP IPv6 subflow child sockets are used. The vulnerable path is specific to MPTCP IPv6; the description does not identify an equivalent issue for non-MPTCP or IPv4-only traffic.

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

A trigger requires concurrent lockless established-hash-table lookups while an MPTCP IPv6 subflow child socket is freed and its kmalloc-backed memory is reused. Exploitation also requires conditions that cause these child sockets to be created and freed; the description does not provide a remote-only trigger.

Q: Why does the issue affect MPTCP IPv6 child sockets?

MPTCP copies the IPv6 TCP protocol definition before its slab cache has been registered, leaving the override's slab pointer unset. As a result, affected child sockets are allocated from kmalloc-4k rather than an RCU-safe TCPv6 slab cache, allowing freed memory to be reused during RCU-protected lookups.

Published Apr 24, 2026

Updated

In the Linux kernel, the following vulnerability has been resolved: mptcp: fix slab-use-after-free in inetlookupestablished The ehash table lookups are lockless and rely on SLABTYPESAFEBYRCU to guarantee socket memory stability during RCU read-side critical sections. Both tcpprot and tcpv6prot have their slab caches created with this flag via protoregister(). However, MPTCP's mptcpsubflowinit() copies tcpv6prot into tcpv6protoverride during inetinit() (fsinitcall, level 5), before inet6init() (moduleinit/deviceinitcall, level 6) has called protoregister(&tcpv6prot). At that point, tcpv6prot.slab is still NULL, so tcpv6protoverride.slab remains NULL permanently. This causes MPTCP v6 subflow child sockets to be allocated via kmalloc (falling into kmalloc-4k) instead of the TCPv6 slab cache. The kmalloc-4k cache lacks SLABTYPESAFEBYRCU, so when these sockets are freed without SOCKRCUFREE (which is cleared for child sockets by design), the memory can be immediately reused. Concurrent ehash lookups under rcureadlock can then access freed memory, triggering a slab-use-after-free in inetlookupestablished. Fix this by splitting the IPv6-specific initialization out of mptcpsubflowinit() into a new mptcpsubflowv6init(), called from mptcpprotov6init() before protocol registration. This ensures tcpv6protoverride.slab correctly inherits the SLABTYPESAFEBYRCU slab cache.

Affected Software

191 affected componentsFixes available

ubuntu/linux-hwe-edge*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-azure*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-oem*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.15<5.15.0-1111.118~20.04.1

5.15.0-1111.118~20.04.1

ubuntu/linux-aws-5.8*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.15<5.15.0-1116.125~20.04.1

5.15.0-1116.125~20.04.1

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-azure-fde-5.15<5.15.0-1116.125~20.04.1

5.15.0-1116.125~20.04.1

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.15<5.15.0-1111.121~20.04.1

5.15.0-1111.121~20.04.1

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<5.15.0-185.195~20.04.1

5.15.0-185.195~20.04.1

ubuntu/linux-hwe-5.8*

ubuntu/linux-ibm-5.15<5.15.0-1105.109~20.04.1

5.15.0-1105.109~20.04.1

ubuntu/linux-intel-5.13*

ubuntu/linux-intel-iotg-5.15<5.15.0-1106.112~20.04.1

5.15.0-1106.112~20.04.1

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-183.193~20.04.1

5.15.0-183.193~20.04.1

ubuntu/linux-nvidia-tegra-5.15<5.15.0-1063.63~20.04.1

5.15.0-1063.63~20.04.1

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-5.15<5.15.0-1108.114~20.04.1

5.15.0-1108.114~20.04.1

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.15<5.15.0-1105.109~20.04.1

5.15.0-1105.109~20.04.1

ubuntu/linux-riscv-5.8*

ubuntu/linux<5.15.0-185.195

5.15.0-185.195

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1111.118

5.15.0-1111.118

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1060.63~22.04.1

6.8.0-1060.63~22.04.1

ubuntu/linux-azure<5.15.0-1116.125

5.15.0-1116.125

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1063.71~22.04.1

6.8.0-1063.71~22.04.1

ubuntu/linux-azure-fde<5.15.0-1116.125

5.15.0-1116.125

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8<6.8.0-1062.69~22.04.1

6.8.0-1062.69~22.04.1

ubuntu/linux-gcp<5.15.0-1111.121

5.15.0-1111.121

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1063.69~22.04.1

6.8.0-1063.69~22.04.1

ubuntu/linux-gke<5.15.0-1107.113

5.15.0-1107.113

ubuntu/linux-gkeop<5.15.0-1094.102

5.15.0-1094.102

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-136.136~22.04.1

6.8.0-136.136~22.04.1

ubuntu/linux-ibm<5.15.0-1105.109

5.15.0-1105.109

ubuntu/linux-ibm-6.8<6.8.0-1060.61~22.04.1

6.8.0-1060.61~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1106.112

5.15.0-1106.112

ubuntu/linux-kvm<5.15.0-1103.108

5.15.0-1103.108

ubuntu/linux-lowlatency<5.15.0-183.193

5.15.0-183.193

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-134.134.1~22.04.1

6.8.0-134.134.1~22.04.1

ubuntu/linux-nvidia<5.15.0-1106.107

5.15.0-1106.107

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1058.61~22.04.1

6.8.0-1058.61~22.04.1

ubuntu/linux-nvidia-tegra<5.15.0-1063.63

5.15.0-1063.63

ubuntu/linux-nvidia-tegra-igx<5.15.0-1052.52

5.15.0-1052.52

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1108.114

5.15.0-1108.114

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1057.58~22.04.1

6.8.0-1057.58~22.04.1

ubuntu/linux-raspi<5.15.0-1105.108

5.15.0-1105.108

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-134.134~22.04.1

6.8.0-134.134~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp<5.15.0-1074.78

5.15.0-1074.78

ubuntu/linux-bluefield<5.15.0-1095.97

5.15.0-1095.97

ubuntu/linux-intel-iot-realtime<5.15.0-1103.105

5.15.0-1103.105

ubuntu/linux-realtime<5.15.0-1110.119

5.15.0-1110.119

ubuntu/linux-realtime-6.8<6.8.1-1055.56~22.04.1

6.8.1-1055.56~22.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1111.118+fips1

5.15.0-1111.118+fips1

ubuntu/linux-azure-fips<5.15.0-1116.125+fips1

5.15.0-1116.125+fips1

ubuntu/linux-fips<5.15.0-185.195+fips1

5.15.0-185.195+fips1

ubuntu/linux-gcp-fips<5.15.0-1111.121+fips1

5.15.0-1111.121+fips1

ubuntu/linux<6.8.0-134.134

6.8.0-134.134

ubuntu/linux-aws<6.8.0-1060.63

6.8.0-1060.63

ubuntu/linux-aws-6.14*

ubuntu/linux-aws-6.17<6.17.0-1019.19~24.04.1

6.17.0-1019.19~24.04.1

ubuntu/linux-azure<6.8.0-1063.71

6.8.0-1063.71

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-6.17<6.17.0-1021.21~24.04.1

6.17.0-1021.21~24.04.1

ubuntu/linux-azure-fde<6.8.0-1062.69

6.8.0-1062.69

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-nvidia*

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1063.69

6.8.0-1063.69

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gcp-6.17<6.17.0-1020.22~24.04.1

6.17.0-1020.22~24.04.1

ubuntu/linux-gke<6.8.0-1058.64

6.8.0-1058.64

ubuntu/linux-gkeop<6.8.0-1045.48

6.8.0-1045.48

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-hwe-6.17<6.17.0-40.40~24.04.1

6.17.0-40.40~24.04.1

ubuntu/linux-ibm<6.8.0-1060.61

6.8.0-1060.61

ubuntu/linux-lowlatency<6.8.0-134.134.1

6.8.0-134.134.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1058.61

6.8.0-1058.61

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17<6.17.0-1026.26

6.17.0-1026.26

ubuntu/linux-nvidia-lowlatency<6.8.0-1058.61.1

6.8.0-1058.61.1

ubuntu/linux-nvidia-tegra<6.8.0-1029.30

6.8.0-1029.30

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17<6.17.0-1028.28

6.17.0-1028.28

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1057.58

6.8.0-1057.58

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17<6.17.0-1018.18~24.04.1

6.17.0-1018.18~24.04.1

ubuntu/linux-raspi<6.8.0-1060.64

6.8.0-1060.64

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-riscv-6.17*

ubuntu/linux-vmware<6.8.0-1008.8

6.8.0-1008.8

ubuntu/linux-xilinx<6.8.0-1032.33

6.8.0-1032.33

ubuntu/linux-bluefield<6.8.0-1026.30

6.8.0-1026.30

ubuntu/linux-raspi-realtime<6.8.0-2049.50

6.8.0-2049.50

ubuntu/linux-realtime<6.8.1-1055.56

6.8.1-1055.56

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17<6.17.0-1017.19~24.04.1

6.17.0-1017.19~24.04.1

ubuntu/linux-aws-fips<6.8.0-1060.63+fips1

6.8.0-1060.63+fips1

ubuntu/linux-azure-fips<6.8.0-1062.69+fips1

6.8.0-1062.69+fips1

ubuntu/linux-fips<6.8.0-134.134+fips1

6.8.0-134.134+fips1

ubuntu/linux-gcp-fips<6.8.0-1063.69+fips1

6.8.0-1063.69+fips1

ubuntu/linux<6.17.0-40.40

6.17.0-40.40

ubuntu/linux-aws<6.17.0-1019.19

6.17.0-1019.19

ubuntu/linux-azure*

ubuntu/linux-azure-fde*

ubuntu/linux-gcp<6.17.0-1020.22

6.17.0-1020.22

ubuntu/linux-oracle<6.17.0-1018.18

6.17.0-1018.18

ubuntu/linux-raspi<6.17.0-1021.21

6.17.0-1021.21

ubuntu/linux-realtime<6.17.0-1017.19

6.17.0-1017.19

ubuntu/linux-riscv<6.17.0-40.40.1

6.17.0-40.40.1

ubuntu/linux-nvidia<7.0.0-1006.6

7.0.0-1006.6

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-aws-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1111.118~20.04.1
Upgrade
Upgrade ubuntu/linux-azure-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1116.125~20.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1116.125~20.04.1
Upgrade
Upgrade ubuntu/linux-gcp-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1111.121~20.04.1
Upgrade
Upgrade ubuntu/linux-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-185.195~20.04.1
Upgrade
Upgrade ubuntu/linux-ibm-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1105.109~20.04.1
Upgrade
Upgrade ubuntu/linux-intel-iotg-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1106.112~20.04.1
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-183.193~20.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1063.63~20.04.1
Upgrade
Upgrade ubuntu/linux-oracle-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1108.114~20.04.1
Upgrade
Upgrade ubuntu/linux-riscv-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1105.109~20.04.1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 5.15.0-185.195
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 5.15.0-1111.118
Upgrade
Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1060.63~22.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 5.15.0-1116.125
Upgrade
Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1063.71~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 5.15.0-1116.125
Upgrade
Upgrade ubuntu/linux-azure-fde-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1062.69~22.04.1
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 5.15.0-1111.121
Upgrade
Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1063.69~22.04.1
Upgrade
Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 5.15.0-1107.113
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 5.15.0-1094.102
Upgrade
Upgrade ubuntu/linux-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-136.136~22.04.1
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 5.15.0-1105.109
Upgrade
Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1060.61~22.04.1
Upgrade
Upgrade ubuntu/linux-intel-iotg to a version that resolves this vulnerability.
Fixed in 5.15.0-1106.112
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 5.15.0-1103.108
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 5.15.0-183.193
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-134.134.1~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 5.15.0-1106.107
Upgrade
Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.61~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 5.15.0-1063.63
Upgrade
Upgrade ubuntu/linux-nvidia-tegra-igx to a version that resolves this vulnerability.
Fixed in 5.15.0-1052.52
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 5.15.0-1108.114
Upgrade
Upgrade ubuntu/linux-oracle-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1057.58~22.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 5.15.0-1105.108
Upgrade
Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-134.134~22.04.1
Upgrade
Upgrade ubuntu/linux-xilinx-zynqmp to a version that resolves this vulnerability.
Fixed in 5.15.0-1074.78
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 5.15.0-1095.97
Upgrade
Upgrade ubuntu/linux-intel-iot-realtime to a version that resolves this vulnerability.
Fixed in 5.15.0-1103.105
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 5.15.0-1110.119
Upgrade
Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1055.56~22.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1111.118+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1116.125+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-185.195+fips1
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1111.121+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-134.134
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.8.0-1060.63
Upgrade
Upgrade ubuntu/linux-aws-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1019.19~24.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.8.0-1063.71
Upgrade
Upgrade ubuntu/linux-azure-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1021.21~24.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 6.8.0-1062.69
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.8.0-1063.69
Upgrade
Upgrade ubuntu/linux-gcp-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1020.22~24.04.1
Upgrade
Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.64
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 6.8.0-1045.48
Upgrade
Upgrade ubuntu/linux-hwe-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-40.40~24.04.1
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 6.8.0-1060.61
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-134.134.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.61
Upgrade
Upgrade ubuntu/linux-nvidia-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1026.26
Upgrade
Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.61.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.30
Upgrade
Upgrade ubuntu/linux-oem-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1028.28
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.8.0-1057.58
Upgrade
Upgrade ubuntu/linux-oracle-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1018.18~24.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.8.0-1060.64
Upgrade
Upgrade ubuntu/linux-vmware to a version that resolves this vulnerability.
Fixed in 6.8.0-1008.8
Upgrade
Upgrade ubuntu/linux-xilinx to a version that resolves this vulnerability.
Fixed in 6.8.0-1032.33
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 6.8.0-1026.30
Upgrade
Upgrade ubuntu/linux-raspi-realtime to a version that resolves this vulnerability.
Fixed in 6.8.0-2049.50
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.8.1-1055.56
Upgrade
Upgrade ubuntu/linux-realtime-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1017.19~24.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1060.63+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1062.69+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-134.134+fips1
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1063.69+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.17.0-40.40
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.17.0-1019.19
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.17.0-1020.22
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.17.0-1018.18
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.17.0-1021.21
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.17.0-1017.19
Upgrade
Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.
Fixed in 6.17.0-40.40.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 7.0.0-1006.6

Event History

Apr 24, 2026

CVE Published

via OSV·03:16 PM

Data Sourced

via OSV·03:16 PM

DescriptionSeverityAffected Software

Frequently Asked Questions

Which systems are exposed to this issue?

The issue affects the listed Ubuntu Linux kernel packages when MPTCP IPv6 subflow child sockets are used. The vulnerable path is specific to MPTCP IPv6; the description does not identify an equivalent issue for non-MPTCP or IPv4-only traffic.

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

A trigger requires concurrent lockless established-hash-table lookups while an MPTCP IPv6 subflow child socket is freed and its kmalloc-backed memory is reused. Exploitation also requires conditions that cause these child sockets to be created and freed; the description does not provide a remote-only trigger.

Why does the issue affect MPTCP IPv6 child sockets?

MPTCP copies the IPv6 TCP protocol definition before its slab cache has been registered, leaving the override's slab pointer unset. As a result, affected child sockets are allocated from kmalloc-4k rather than an RCU-safe TCPv6 slab cache, allowing freed memory to be reused during RCU-protected lookups.

UBUNTU-CVE-2026-31669: Use After Free

Affected Software

Remediation

Event History

Frequently Asked Questions

Which systems are exposed to this issue?

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

Why does the issue affect MPTCP IPv6 child sockets?

Company

Resources

Contact