CVE-2026-72137

Published Aug 15, 2026

Last updated 2 months ago

CVSS critical 9.8
Linux Kernel
Xfrm

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-72137 describes a double-free error found within the Linux kernel's NAT keep-alive implementation. This vulnerability occurs when the `nat_keepalive_send()` function attempts to free a socket buffer (skb) twice. This happens if a send helper reports an error after the packet has already been passed to the output path, where the networking stack might have already consumed and freed the skb. This flaw can lead to undefined memory handling, potentially resulting in memory corruption, a kernel crash, or other unpredictable system behavior. All Linux kernel releases that incorporate the `nat_keepalive_send` path, including both IPv4 and IPv6 stacks, are potentially affected by this issue.

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.
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Received

Risk scores

CVSS 3.1

Type
Secondary
Base score
9.8
Impact score
5.9
Exploitability score
3.9
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity
CRITICAL

Social media

Hype score
Not currently trending

  1. For oss-sec: CVE-2026-72137 needs xfrm, CVE-2026-52933 needs io_uring, CVE-2026-52929 needs sctp, CVE-2026-43502 needs rds (is what the original post was about)

    @spendergrsec

    8 Sept 2026

    668 Impressions

    0 Retweets

    4 Likes

    2 Bookmarks

    0 Replies

    0 Quotes

  2. Aug 26: Today's exploit is for the latest Ubuntu 26.04, a double free in xfrm: CVE-2026-72137. It was introduced in Jun 2024 and fixed upstream in Jul 2026. Discovered and exploited by the NebuSec security pipeline. Exp source code: https://t.co/pdWe5TbDCT https://t.co/Ksqrj1G

    @cybermeowfia

    31 Aug 2026

    2126 Impressions

    7 Retweets

    23 Likes

    5 Bookmarks

    0 Replies

    0 Quotes

  3. Today's exploit is for the latest Ubuntu 26.04, a double free in xfrm: CVE-2026-72137. It was introduced in Jun 2024 and fixed upstream in Jul 2026. Discovered and exploited by the NebuSec security pipeline. Exploit source code: https://t.co/dT3jB4J1sM https://t.co/Hq4Vy0qIIo

    @nebusecurity

    27 Aug 2026

    20550 Impressions

    17 Retweets

    101 Likes

    54 Bookmarks

    0 Replies

    3 Quotes

Related CVEs

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References

Sources include official advisories and independent security research.