Linux Kernel seg6 lwtunnel dst_cache split to fix SID lookup bypass
CVE-2026-31668 Published on April 24, 2026
seg6: separate dst_cache for input and output paths in seg6 lwtunnel
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.
Products Associated with CVE-2026-31668
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Affected Versions
Linux:- Version 6c8702c60b88651072460f3f4026c7dfe2521d12 and below 1dec91d3b1cefb82635761b7812154af3ef46449 is affected.
- Version 6c8702c60b88651072460f3f4026c7dfe2521d12 and below 750569d6987a0ff46317a4b86eb3907e296287bf is affected.
- Version 6c8702c60b88651072460f3f4026c7dfe2521d12 and below 57d0374d14fa667dec6952173b93e7e84486d5c9 is affected.
- Version 6c8702c60b88651072460f3f4026c7dfe2521d12 and below 84d458018b147176b259347103fccb7e93abd2b1 is affected.
- Version 6c8702c60b88651072460f3f4026c7dfe2521d12 and below 6305ad032b03d2ea4181b953a66e19a9a6ed053c is affected.
- Version 6c8702c60b88651072460f3f4026c7dfe2521d12 and below fb56de5d99218de49d5d43ef3a99e062ecd0f9a1 is affected.
- Version 6c8702c60b88651072460f3f4026c7dfe2521d12 and below 17d87d42874f5d6c1a0ccc6d9190dfe82a9a7a6a is affected.
- Version 6c8702c60b88651072460f3f4026c7dfe2521d12 and below c3812651b522fe8437ebb7063b75ddb95b571643 is affected.
- Version 4.10 is affected.
- Before 4.10 is unaffected.
- Version 5.10.253, <= 5.10.* is unaffected.
- Version 5.15.203, <= 5.15.* is unaffected.
- Version 6.1.169, <= 6.1.* is unaffected.
- Version 6.6.135, <= 6.6.* is unaffected.
- Version 6.12.82, <= 6.12.* is unaffected.
- Version 6.18.23, <= 6.18.* is unaffected.
- Version 6.19.13, <= 6.19.* is unaffected.
- Version 7.0, <= * is unaffected.