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VulnerabilityPublished Updated

CVE-2026-31668: Linux kernel · seg6: separate dst_cache for input and output paths in seg6 lwtunnel

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.8 Critical · fixed in fb56de5d99218de49d5d43ef3a99e062ecd0f9a1 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 38% 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 fb56de5d99218de49d5d43ef3a99e062ecd0f9a1, c3812651b522fe8437ebb7063b75ddb95b571643, 750569d6987a0ff46317a4b86eb3907e296287bf +5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 6c8702c60b88651072460f3f4026c7dfe2521d12, < fb56de5d99218de49d5d43ef3a99e062ecd0f9a1
Fixed in
  • fb56de5d99218de49d5d43ef3a99e062ecd0f9a1
LinuxLinuxAffected
  • ≥ 6c8702c60b88651072460f3f4026c7dfe2521d12, < c3812651b522fe8437ebb7063b75ddb95b571643
Fixed in
  • c3812651b522fe8437ebb7063b75ddb95b571643
LinuxLinuxAffected
  • ≥ 6c8702c60b88651072460f3f4026c7dfe2521d12, < 750569d6987a0ff46317a4b86eb3907e296287bf
Fixed in
  • 750569d6987a0ff46317a4b86eb3907e296287bf
LinuxLinuxAffected
  • ≥ 6c8702c60b88651072460f3f4026c7dfe2521d12, < 6305ad032b03d2ea4181b953a66e19a9a6ed053c
Fixed in
  • 6305ad032b03d2ea4181b953a66e19a9a6ed053c
LinuxLinuxAffected
  • ≥ 6c8702c60b88651072460f3f4026c7dfe2521d12, < 84d458018b147176b259347103fccb7e93abd2b1
Fixed in
  • 84d458018b147176b259347103fccb7e93abd2b1
LinuxLinuxAffected
  • ≥ 6c8702c60b88651072460f3f4026c7dfe2521d12, < 57d0374d14fa667dec6952173b93e7e84486d5c9
Fixed in
  • 57d0374d14fa667dec6952173b93e7e84486d5c9

AI-suggested

A fix is available and has been applied in multiple Linux kernel commits as listed in the fixedVersions. Users and administrators should update to a Linux kernel version that includes these fixes to mitigate the vulnerability.

Description

CVE-2026-31668 is a critical vulnerability in the Linux kernel's seg6 lwtunnel implementation. The issue arises because a single destination cache (dst_cache) is shared between input and output paths, which can lead to incorrect routing decisions due to cache reuse across different routing contexts. This flaw has been fixed by separating the cache into distinct input and output caches to maintain independent routing lookups.

References

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