Release of Invalid Pointer or Reference Affecting kernel-64k-debug-devel-matched package, versions *


Severity

Recommended
0.0
high
0
10

Based on CentOS security rating.

Threat Intelligence

EPSS
0.03% (9th percentile)

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  • Snyk IDSNYK-CENTOS9-KERNEL64KDEBUGDEVELMATCHED-16271660
  • published25 Apr 2026
  • disclosed24 Apr 2026

Introduced: 24 Apr 2026

NewCVE-2026-31669  (opens in a new tab)
CWE-763  (opens in a new tab)

How to fix?

There is no fixed version for Centos:9 kernel-64k-debug-devel-matched.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-64k-debug-devel-matched package and not the kernel-64k-debug-devel-matched package as distributed by Centos. See How to fix? for Centos:9 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

mptcp: fix slab-use-after-free in __inet_lookup_established

The ehash table lookups are lockless and rely on SLAB_TYPESAFE_BY_RCU to guarantee socket memory stability during RCU read-side critical sections. Both tcp_prot and tcpv6_prot have their slab caches created with this flag via proto_register().

However, MPTCP's mptcp_subflow_init() copies tcpv6_prot into tcpv6_prot_override during inet_init() (fs_initcall, level 5), before inet6_init() (module_init/device_initcall, level 6) has called proto_register(&tcpv6_prot). At that point, tcpv6_prot.slab is still NULL, so tcpv6_prot_override.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 SLAB_TYPESAFE_BY_RCU, so when these sockets are freed without SOCK_RCU_FREE (which is cleared for child sockets by design), the memory can be immediately reused. Concurrent ehash lookups under rcu_read_lock can then access freed memory, triggering a slab-use-after-free in __inet_lookup_established.

Fix this by splitting the IPv6-specific initialization out of mptcp_subflow_init() into a new mptcp_subflow_v6_init(), called from mptcp_proto_v6_init() before protocol registration. This ensures tcpv6_prot_override.slab correctly inherits the SLAB_TYPESAFE_BY_RCU slab cache.

CVSS Base Scores

version 3.1