xfrm: nat_keepalive: avoid double free on send error (CVE-2026-72137) | HOL Guard CVE

Critical · CVSS 9.8CVE-2026-72137

xfrm: nat_keepalive: avoid double free on send error

Answer in brief

CVE-2026-72137 records a Critical severity (CVSS 9.8) vulnerability in xfrm: nat_keepalive: avoid double free on send error. 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 Aug 15, 2026Updated Aug 17, 2026Source checked Sep 29, 2026First seen by HOL Aug 15, 2026Material review Aug 17, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.8
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

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.

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	>=f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae <d0a4dc7efa825bce60a8da8f7d43c864a159abde \|\| >=f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae <5b0c4c916f202b8fd13d12afb6af62b385622f81 \|\| >=f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae <a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693 \|\| >=f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae <226f4a490d1a938fc838d8f8c46a4eca864c0d78	d0a4dc7efa825bce60a8da8f7d43c864a159abde, 5b0c4c916f202b8fd13d12afb6af62b385622f81, a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693, 226f4a490d1a938fc838d8f8c46a4eca864c0d78
Linux/Linuxgeneric	6.11	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to d0a4dc7efa825bce60a8da8f7d43c864a159abde if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 17, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 15, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: xfrm: nat_keepalive: avoid double free on send error nat_keepalive_send() frees the keepalive skb whenever the IPv4 or IPv6 send helper reports an error. That cleanup is only correct before the skb is handed to the output path. Once ip_build_and_send_pkt() or ip6_xmit() takes ownership, the networking stack may already have consumed the skb before returning an error, so freeing it again is unsafe. Handle the pre-handoff failure cases inside nat_keepalive_send_ipv4() and nat_keepalive_send_ipv6(), where the caller still owns the skb, and keep nat_keepalive_send() responsible only for family dispatch and the unsupported-family cleanup path.

Quoted source text, attributed separately from HOL analysis.