{"id":"CVE-2026-80634","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag\n\nThe DEV_PATH_BR_VLAN_UNTAG case post-decrements info->num_encaps\ninside WARN_ON_ONCE()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag\n\nThe DEV_PATH_BR_VLAN_UNTAG case post-decrements info->num_encaps\ninside WARN_ON_ONCE(). num_encap…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","published":"2026-08-28","updated":"2026-08-29","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-80634","references":[{"url":"https://git.kernel.org/stable/c/2f55fa28011c97d6495d5787808db10a8c2d690d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e052f920773b73be49eb4d8702a9f85de7464363","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00553,"epssPercentile":0.43776,"ingestedAt":"2026-08-30T03:46:31.052Z","slug":"CVE-2026-80634","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag\n\nThe DEV_PATH_BR_VLAN_UNTAG case post-decrements info->num_encaps\ninside WARN_ON_ONCE(). num_encaps is u8, so if it's already 0 the\ndecrement still happens and wraps it to 255. The break only leaves\nthe inner switch -- a later path entry can set info->indev back to\na real device, and we end up returning with num_encaps == 255.\n\nnft_dev_forward_path() then walks info.encap[] (size 2) up to\nnum_encaps, which means an OOB stack read and a bogus count copied\ninto the route descriptor.\n\nShould only happen on a malformed bridge path stack, hence the WARN,\nbut worth handling sanely. Move the decrement out of the WARN.\n\n[ While at this, remove the WARN_ON_ONCE since this can only happen\n  with a buggy bridge path stack --pablo ].\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}