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Not in CISA KEV
HIGH severity

CVE-2026-12413 — libreswan

HIGH

CVE-2026-12413 is a high-severity (CVSS 7.5) CWE-193 vulnerability. A fix is available — see the affected versions and patch details below.

Published
Jul 2, 2026
Updated
Jul 27, 2026
Affected
1 product
Patched
See advisory
Exploits
None indexed
Exploitation data as of Sep 29, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-12413.

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs47th percentile — riskier than 47% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-12413 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 380,526 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Description

An invalidly formatted IKEv2 fragment causes the Libreswan pluto daemon to crash and restart. Continued exploitation would cause a denial of service. The function reassemble_v2_incoming_fragments() would ignore unknown outer payloads but still store these in a fixed size array msg_digest.digest[PAYLIMIT]. An off-by-one error in the assertion PASSERT(logger, md->digest_roof < elemsof(md->digest)) causes the daemon to abort. No remote code execution is possible. Any configuration that allows IKEv2 connections that do not set fragmentation=no are vulnerable. IKEv1 is not affected.

Affected Products

1 product · 1 configurations
Application
libreswanlibreswan
≥ 4.6 && < 5.3.1
range

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Fix

    Upgrade the affected component to the fixed release for CVE-2026-12413, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Red Hat Product Security rates this vulnerability as having an Important impact, primarily because it can be exploited remotely without authentication. However, the actual exposure depends entirely on your specific VPN configuration: ``` Affected Configurations: This vulnerability only impacts IKEv2 connections. By…

Workaround published by Red Hat
If upgrading to Libreswan is not an option, you can mitigate the vulnerability by disabling IKEv2 fragment processing: Add the following directive to your global or connection-specific configuration files in /etc/ipsec.conf: ```fragmentation=no``` Warning: Disabling fragmentation may cause larger IKEv2 payloads (such as those carrying large X.509 certificate chains) to be dropped by intermediate network routers if they exceed the path MTU.
Source: Red Hat security advisory for CVE-2026-12413 (CC BY 4.0)
ProductFixed inAdvisory
Fast Datapath for Red Hat Enterprise Linux 9libreswan-0:5.3.2-1.el9fdpRHSA-2026:46986
Red Hat Enterprise Linux 10libreswan-0:5.3.2-1.el10_2RHSA-2026:46398
Red Hat Enterprise Linux 10.0 Extended Update Supportlibreswan-0:5.2-1.el10_0.5RHSA-2026:55449
Red Hat Enterprise Linux 8libreswan-0:4.12-2.el8_10.6RHSA-2026:46396
Red Hat Enterprise Linux 8.8 Telecommunications Update Servicelibreswan-0:4.9-3.el8_8.3RHSA-2026:72287
Red Hat Enterprise Linux 9libreswan-0:4.15-10.el9_8RHSA-2026:46397
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutionslibreswan-0:4.9-5.el9_2.5RHSA-2026:61779
Red Hat Enterprise Linux 9.4 Update Services for SAP Solutionslibreswan-0:4.12-3.el9_4.2RHSA-2026:61258

Frequently Asked Questions

An invalidly formatted IKEv2 fragment causes the Libreswan pluto daemon to crash and restart. Continued exploitation would cause a denial of service. The function reassemble_v2_incoming_fragments() would ignore unknown outer payloads but still store these in a fixed size array msg_digest.digest[PAYLIMIT]. An off-by-one error in the assertion PASSERT(logger, md->digest_roof < elemsof(md->digest)) causes the daemon to abort. No remote code execution is possible. Any configuration that allows IKEv2 connections that do not set fragmentation=no are vulnerable. IKEv1 is not affected.
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CVE-2026-12413: libreswan RCE (High 7.5) | O3 Security