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CVE-2026-80634: Linux

Severity

9.8 (CRITICAL)

Vendor

LINUX

Affected versions

e990cef6516daa4e1e236433579e333f74fd38cb through before 2f55fa28011c97d6495d5787808db10a8c2d690d; e990cef6516daa4e1e2364

Patch status

Patched

Published

2026-08-28T08:16:48.303

Modified

2026-08-29T07:16:47.430

Why it matters

Critical vulnerability requiring immediate validation against your environment.

Recommended admin actions

• Prioritize validation immediately due to critical CVSS severity.

Technical summary

In the Linux kernel, the following vulnerability has been resolved: netfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag The DEV_PATH_BR_VLAN_UNTAG case post-decrements info->num_encaps inside WARN_ON_ONCE(). num_encaps is u8, so if it's already 0 the decrement still happens and wraps it to 255. The break only leaves the inner switch — a later path entry can set info->indev back to a real device, and we end up returning with num_encaps == 255. nft_dev_forward_path() then walks info.encap[] (size 2) up to num_encaps, which means an OOB stack read and a bogus count copied into the route descriptor. Should only happen on a malformed bridge path stack, hence the WARN, but worth handling sanely. Move the decrement out of the WARN. [ While at this, remove the WARN_ON_ONCE since this can only happen with a buggy bridge path stack –pablo ].

View the official NVD record for CVE-2026-80634

CVE data is sourced from NVD/CNA records and optional enrichment. Validate against the vendor advisory before taking production action.