CVE-2026-31669: Linux kernel · mptcp: fix slab-use-after-free in __inet_lookup_established
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 9.8 Critical · fixed in fb1f54b7d16f393b8b65d328410f78b4beea8fcc : patch Linux kernel as a priority.
Data as of 26 Oct 2026, 17:30 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 40% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers can reliably automate steps 1–4 of the kill chain
- Technical impact
- Total control over the software or total information disclosure
CISA SSVC assessment, 2026-10-16.
- Patch
- Available – fixed in fb1f54b7d16f393b8b65d328410f78b4beea8fcc, f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47, eb9c6aeb512f877cf397deb1e4526f646c70e4a7 +4
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 24 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
AI-suggested
A fix is available and has been applied in the Linux kernel source code as indicated by the listed fixed commit versions. Users and administrators should update their Linux kernel to a version that includes these fixes to remediate the vulnerability. No additional mitigation steps are indicated by the vendor advisory.
Description
CVE-2026-31669 is a critical use-after-free vulnerability in the Linux kernel's multipath TCP (MPTCP) implementation affecting version 5.12. It arises from improper initialization of the tcpv6_prot_override slab cache, causing IPv6 MPTCP subflow child sockets to be allocated without the SLAB_TYPESAFE_BY_RCU flag. This leads to potential memory reuse and concurrent access to freed memory during ehash lookups, resulting in a slab-use-after-free in __inet_lookup_established. The issue is fixed by properly initializing the slab cache before protocol registration.
References
- git.kernel.org/stable/c/f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47 (opens in a new tab)
- git.kernel.org/stable/c/fb1f54b7d16f393b8b65d328410f78b4beea8fcc (opens in a new tab)
- git.kernel.org/stable/c/3fd6547f5b8ac99687be6d937a0321efda760597 (opens in a new tab)
- git.kernel.org/stable/c/eb9c6aeb512f877cf397deb1e4526f646c70e4a7 (opens in a new tab)
- git.kernel.org/stable/c/15fa9ead4d5e6b6b9c794e84144146c917f2cb62 (opens in a new tab)
- git.kernel.org/stable/c/b313e9037d98c13938740e5ebda7852929366dff (opens in a new tab)
- git.kernel.org/stable/c/9b55b253907e7431210483519c5ad711a37dafa1 (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-082556.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)