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9.8
CRITICAL CVSS 3.1
CVE-2026-72137
xfrm: nat_keepalive: avoid double free on send error
Overview
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.

Details
INFO

Published Date :

Aug. 15, 2026, 6:21 a.m.

Last Modified :

Aug. 17, 2026, 6:18 a.m.

Remotely Exploit :

Yes !

Source :

416baaa9-dc9f-4396-8d5f-8c081fb06d67
Impact
Affected Products

The following products are affected by CVE-2026-72137 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Linux linux_kernel
: Total Affected Vendor : 1 | Products : 1
Scoring
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 3.1 CRITICAL 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
Correctly handle skb ownership to prevent double free errors.
  • Apply the Linux kernel patch for the xfrm: nat_keepalive issue.
  • Handle pre-handoff failures within IPv4 and IPv6 send functions.
  • Ensure skb cleanup occurs only when ownership is maintained.
References
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-72137.

URL Resource
https://git.kernel.org/stable/c/226f4a490d1a938fc838d8f8c46a4eca864c0d78
https://git.kernel.org/stable/c/5b0c4c916f202b8fd13d12afb6af62b385622f81
https://git.kernel.org/stable/c/a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693
https://git.kernel.org/stable/c/d0a4dc7efa825bce60a8da8f7d43c864a159abde
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-72137 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-72137 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-72137 vulnerability anywhere in the article.

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2026-72137 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Aug. 17, 2026

    Action Type Old Value New Value
    Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    Changed Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': 'd0a4dc7efa825bce60a8da8f7d43c864a159abde', 'versionType': 'git'}, {'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': '5b0c4c916f202b8fd13d12afb6af62b385622f81', 'versionType': 'git'}, {'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': 'a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693', 'versionType': 'git'}, {'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': '226f4a490d1a938fc838d8f8c46a4eca864c0d78', 'versionType': 'git'}], 'programFiles': ['net/xfrm/xfrm_nat_keepalive.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.11'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.11', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.12.101', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.40', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.1.5', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2-rc4', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['net/xfrm/xfrm_nat_keepalive.c'], 'defaultStatus': 'affected'}] [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': 'd0a4dc7efa825bce60a8da8f7d43c864a159abde', 'versionType': 'git'}, {'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': '5b0c4c916f202b8fd13d12afb6af62b385622f81', 'versionType': 'git'}, {'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': 'a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693', 'versionType': 'git'}, {'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': '226f4a490d1a938fc838d8f8c46a4eca864c0d78', 'versionType': 'git'}], 'programFiles': ['net/xfrm/xfrm_nat_keepalive.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.11'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.11', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.12.101', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.40', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.1.5', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['net/xfrm/xfrm_nat_keepalive.c'], 'defaultStatus': 'affected'}]
  • New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Aug. 15, 2026

    Action Type Old Value New Value
    Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': 'd0a4dc7efa825bce60a8da8f7d43c864a159abde', 'versionType': 'git'}, {'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': '5b0c4c916f202b8fd13d12afb6af62b385622f81', 'versionType': 'git'}, {'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': 'a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693', 'versionType': 'git'}, {'status': 'affected', 'version': 'f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae', 'lessThan': '226f4a490d1a938fc838d8f8c46a4eca864c0d78', 'versionType': 'git'}], 'programFiles': ['net/xfrm/xfrm_nat_keepalive.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.11'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.11', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.12.101', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.40', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.1.5', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2-rc4', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['net/xfrm/xfrm_nat_keepalive.c'], 'defaultStatus': 'affected'}]
    Added 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.
    Added Reference https://git.kernel.org/stable/c/226f4a490d1a938fc838d8f8c46a4eca864c0d78
    Added Reference https://git.kernel.org/stable/c/5b0c4c916f202b8fd13d12afb6af62b385622f81
    Added Reference https://git.kernel.org/stable/c/a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693
    Added Reference https://git.kernel.org/stable/c/d0a4dc7efa825bce60a8da8f7d43c864a159abde
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CVSS
Vulnerability Scoring Details
Base CVSS Score: 9.8
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