CVE-2026-31669

Advisory lineage Upstream: 0 Downstream: 24
Analyzed
Published: 24 Apr 2026, 14:45
Last modified:14 Jul 2026, 12:48

Vulnerability Summary

Overall Risk (default)
high
70/100
CVSS Score
9.8 CRITICAL
v3.1 (cve.org)
EPSS Score
0.4% LOW
0% probability 0.00%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

24 Apr 2026, 14:45
Published
Vulnerability first disclosed
14 Jul 2026, 12:48
Last Modified
Vulnerability information updated

Description

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 Metrics

  • v3.1•CRITICAL•Score: 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Trends

Current EPSS score: 0.40%• Percentile: 32%

Techniques & Countermeasures

  • CWE-416•Use After Free

    The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Affected Systems

  • linux•linux

    ≥ b19bc2945b40b9fd38e835700907ffe8534ef0de, < f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47 | ≥ b19bc2945b40b9fd38e835700907ffe8534ef0de, < fb1f54b7d16f393b8b65d328410f78b4beea8fcc | ≥ b19bc2945b40b9fd38e835700907ffe8534ef0de, < 3fd6547f5b8ac99687be6d937a0321efda760597 | ≥ b19bc2945b40b9fd38e835700907ffe8534ef0de, < eb9c6aeb512f877cf397deb1e4526f646c70e4a7 | ≥ b19bc2945b40b9fd38e835700907ffe8534ef0de, < 15fa9ead4d5e6b6b9c794e84144146c917f2cb62 | ≥ b19bc2945b40b9fd38e835700907ffe8534ef0de, < b313e9037d98c13938740e5ebda7852929366dff | ≥ b19bc2945b40b9fd38e835700907ffe8534ef0de, < 9b55b253907e7431210483519c5ad711a37dafa1 | 5.12

  • linux•linux kernel

    ≥ 5.12.1, < 5.15.203 | ≥ 5.16, < 6.1.169 | ≥ 6.2, < 6.6.135 | ≥ 6.7, < 6.12.82 | ≥ 6.13, < 6.18.23 | ≥ 6.19, < 6.19.13 | 5.12 | 7.0:rc1 | 7.0:rc2 | 7.0:rc3 | 7.0:rc4 | 7.0:rc5 | 7.0:rc6 | 7.0:rc7

References (9)