CVE-2026-31668: Linux kernel · seg6: separate dst_cache for input and output paths in seg6 lwtunnel
Affects Linux kernelSource CVE Database V5
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
- 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: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
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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
- git.kernel.org/stable/c/1dec91d3b1cefb82635761b7812154af3ef46449 (opens in a new tab)
- git.kernel.org/stable/c/750569d6987a0ff46317a4b86eb3907e296287bf (opens in a new tab)
- git.kernel.org/stable/c/57d0374d14fa667dec6952173b93e7e84486d5c9 (opens in a new tab)
- git.kernel.org/stable/c/84d458018b147176b259347103fccb7e93abd2b1 (opens in a new tab)
- git.kernel.org/stable/c/6305ad032b03d2ea4181b953a66e19a9a6ed053c (opens in a new tab)
- git.kernel.org/stable/c/fb56de5d99218de49d5d43ef3a99e062ecd0f9a1 (opens in a new tab)
- git.kernel.org/stable/c/17d87d42874f5d6c1a0ccc6d9190dfe82a9a7a6a (opens in a new tab)
- git.kernel.org/stable/c/c3812651b522fe8437ebb7063b75ddb95b571643 (opens in a new tab)