CVE-2026-31668

Description

In the Linux kernel, the following vulnerability has been resolved: seg6: separate dst_cache for input and output paths in seg6 lwtunnel The seg6 lwtunnel uses a single dst_cache per encap route, shared between seg6_input_core() and seg6_output_core(). These two paths can perform the post-encap SID lookup in different routing contexts (e.g., ip rules matching on the ingress interface, or VRF table separation). Whichever path runs first populates the cache, and the other reuses it blindly, bypassing its own lookup. Fix this by splitting the cache into cache_input and cache_output, so each path maintains its own cached dst independently.

CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0007

Probability of exploitation

0.21%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.10.1 — 5.10.253
linux	linux_kernel	5.11 — 5.15.203
linux	linux_kernel	5.16 — 6.1.169
linux	linux_kernel	6.2 — 6.6.135
linux	linux_kernel	6.7 — 6.12.82
linux	linux_kernel	6.13 — 6.18.23
linux	linux_kernel	6.19 — 6.19.13
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/17d87d42874f5d6c1a0ccc6d9190dfe82a9a7a6a https://git.kernel.org/stable/c/1dec91d3b1cefb82635761b7812154af3ef46449 https://git.kernel.org/stable/c/57d0374d14fa667dec6952173b93e7e84486d5c9 https://git.kernel.org/stable/c/6305ad032b03d2ea4181b953a66e19a9a6ed053c https://git.kernel.org/stable/c/750569d6987a0ff46317a4b86eb3907e296287bf https://git.kernel.org/stable/c/84d458018b147176b259347103fccb7e93abd2b1 https://git.kernel.org/stable/c/c3812651b522fe8437ebb7063b75ddb95b571643 https://git.kernel.org/stable/c/fb56de5d99218de49d5d43ef3a99e062ecd0f9a1

Frequently Asked Questions

What is CVE-2026-31668? +

In the Linux kernel, the following vulnerability has been resolved: seg6: separate dst_cache for input and output paths in seg6 lwtunnel The seg6 lwtunnel uses a single dst_cache per encap route, shared between seg6_input_core() and seg6_output_core(). These two paths can perform the post-encap SID lookup in different routing contexts (e.g., ip rules matching on the ingress interface, or VRF table separation). Whichever path runs first populates the cache, and the other reuses it blindly, bypassing its own lookup. Fix this by splitting the cache into cache_input and cache_output, so each path maintains its own cached dst independently. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-31668? +

CVE-2026-31668 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0007, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-31668? +

CVE-2026-31668 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-31668? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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