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Linux Kernel CVE-2026-80634

| EUVDEUVD-2026-67510 CRITICAL
2026-08-28 Linux GHSA-jm3q-xwgv-hgh8
Information Disclosure Linux Red Hat Suse
Critical
Disputed · 9.8 Vendor: Linux
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Severity by source

Sources disagree (Medium–Critical)
Vendor (Linux) PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
3.0 LOW

Requires local CAP_NET_ADMIN control to build a malformed bridge/flowtable path (AV:L, PR:H), the malformed-stack precondition makes it AC:H, and impact is a bounded OOB stack read (C:L, A:L).

3.1 AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:L
4.0 AV:L/AC:H/AT:N/PR:H/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
SUSE
6.3 HIGH
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H
Red Hat
5.5 MEDIUM
qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: Linux

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

5
Analysis Generated
Aug 29, 2026 - 07:39 vuln.today
CVSS changed
Aug 29, 2026 - 07:22 NVD
9.8 (CRITICAL)
Patch available
Aug 28, 2026 - 09:02 EUVD
CVE Published
Aug 28, 2026 - 06:48 cve.org
CRITICAL 9.8
CVE Published
Aug 28, 2026 - 06:48 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

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 ].

AnalysisAI

Out-of-bounds stack read in the Linux kernel's netfilter flowtable (nf_flow_table / nft_dev_forward_path) affects the bridge VLAN-untag fast path, where a u8 num_encaps counter can underflow from 0 to 255 and cause the kernel to walk a fixed 2-entry encap[] array far past its bounds. Affected are kernels from 5.13 onward that use netfilter flowtable offload over bridge devices; the flaw leaks adjacent kernel stack memory into a route descriptor and copies a bogus encap count. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires the netfilter flowtable offload code to process a malformed/buggy bridge path stack that hits the DEV_PATH_BR_VLAN_UNTAG case while info->num_encaps is already 0, followed by a later path entry that restores info->indev to a real device. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The supplied CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N, C:H/I:H/A:H = 9.8) is inconsistent with the description and should be treated with skepticism. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upstream fix available (PR/commit); released patched version not independently confirmed - apply the stable-tree commits at https://git.kernel.org/stable/c/e052f920773b73be49eb4d8702a9f85de7464363 and https://git.kernel.org/stable/c/2f55fa28011c97d6495d5787808db10a8c2d690d, which move the num_encaps decrement out of WARN_ON_ONCE() and drop the WARN. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours: identify all Linux systems running kernel version 5.13 or later using uname -r and audit for netfilter and bridge configurations via lsmod | grep nf_flow_table; document which systems are externally exposed or handle sensitive network traffic. …

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 16.0 Affected

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CVE-2026-80634 vulnerability details – vuln.today
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