Answer in brief
CVE-2026-80634 records a Critical severity (CVSS 9.8) vulnerability in netfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=e990cef6516daa4e1e236433579e333f74fd38cb <2f55fa28011c97d6495d5787808db10a8c2d690d || >=e990cef6516daa4e1e236433579e333f74fd38cb <e052f920773b73be49eb4d8702a9f85de7464363 | 2f55fa28011c97d6495d5787808db10a8c2d690d, e052f920773b73be49eb4d8702a9f85de7464363 |
| Linux/Linuxgeneric | 5.13 | Not reported |
Published upstream
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 29, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 28, 2026
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 ].
Quoted source text, attributed separately from HOL analysis.