net: cap advertised IP tunnel headroom

Answer in brief

CVE-2026-80978 records a Unknown severity vulnerability in net: cap advertised IP tunnel headroom. 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.

Published Sep 11, 2026Updated Sep 11, 2026Source checked Sep 11, 2026First seen by HOL Sep 11, 2026Material review Sep 11, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. 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.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=1a37e412a0225fcba5587f24c0dfc7636efc8b69 <bc4e05ae66c9797a0972ac44326e69c5305e0020 \|\| >=1a37e412a0225fcba5587f24c0dfc7636efc8b69 <af0ee8f04bea22cdb331fa3509e17f81b48938ad \|\| >=1a37e412a0225fcba5587f24c0dfc7636efc8b69 <9144f2c53a04465a6878172b523f640313c5559e \|\| >=1a37e412a0225fcba5587f24c0dfc7636efc8b69 <6b222adeb9340306e2ff97127c76117abb9b3df8	bc4e05ae66c9797a0972ac44326e69c5305e0020, af0ee8f04bea22cdb331fa3509e17f81b48938ad, 9144f2c53a04465a6878172b523f640313c5559e, 6b222adeb9340306e2ff97127c76117abb9b3df8
Linux/Linuxgeneric	3.11	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to bc4e05ae66c9797a0972ac44326e69c5305e0020 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 11, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: net: cap advertised IP tunnel headroom IP tunnel devices derive their advertised needed_headroom from lower output devices. A stack of user-created devices can make the derived value larger than the 16-bit skb header offsets can represent. Once IP output reserves it, skb head expansion can wrap those offsets. The runtime transmit path already caps a growing needed_headroom at 512. Apply the same cap when tunnel configuration publishes needed_headroom derived from a lower output device. Capping the advertised value is safe: IP tunnel transmit still expands the skb when a packet needs more headroom. A nonsensical stacked configuration can therefore incur an extra reallocation, but it cannot publish an unbounded reservation to upper layers.

Quoted source text, attributed separately from HOL analysis.