Critical Linux Kernel Netfilter Vulnerability Scores 9.8 CVSS

Last refreshed2026-10-15

Status: UPDATED | Advisory ID: CVE-2026-80634

Key Details

CVE	CVE-2026-80634
CVSS Score / Version	9.8 (Critical) / CVSS v3.1
Updated	2026-10-15
CVSS Vector	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`
CVSS Prose	attack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is unchanged; confidentiality impact is high; integrity impact is high; availability impact is high.
Affected products	Linux Kernel
Exploitation prediction (EPSS)	0.55% probability of exploitation in the next 30 days (45% percentile) -- FIRST.org's EPSS model.

Vendor	Product	Affected Versions	Patch Status
Linux	Linux Kernel

Vendor

Product

Affected Versions

Patch Status

Linux

Linux Kernel

Subsystems	OT Supporting Infrastructure
Sectors	All Sectors

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 ]. (NVD)

Monitor Linux's web page for any future patch releases.

Source	Reference
NVD	https://nvd.nist.gov/vuln/detail/CVE-2026-80634
CVE	https://www.cve.org/CVERecord?id=CVE-2026-80634

Source

Reference

NVD

CVE