CVE-2026-12413: An invalidly formatted IKEv2 fragment causes the Libreswan pluto daemon to crash and restart

This month

HIGH 7.5REMOTEUPGRADE

CVE-2026-12413 is a high-severity flaw (CVSS 7.5) affecting libreswan. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 executio

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 52%)
CISA exploited list	No
Weakness	CWE-193, CWE-617
Published	2026-07-02
Last modified	2026-10-25

Publisher (CNA): Libreswan Project · Vendor: libreswan

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-02 22:16 UTCPublished CVE record published
2026-10-25 21:10 UTCUpdated Record last modified

libreswan libreswan UPGRADE

Affected: >= 4.6 and < 5.3.1

Fixed in: 5.3.1

Safe to downgrade to: a release before 4.6

1. Check installed version

apt-cache policy libreswan || rpm -q libreswan || libreswan --version

2. UPGRADE to 5.3.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libreswan

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libreswan

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 4.6 (Debian / Ubuntu)

apt-cache madison libreswan sudo apt install libreswan=<VERSION_BEFORE_4.6> sudo apt-mark hold libreswan

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list libreswan sudo dnf downgrade libreswan-<VERSION_BEFORE_4.6> sudo dnf versionlock add libreswan

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-12413?

libreswan: upgrade to 5.3.1. Exact commands for each OS are on this page.

Is CVE-2026-12413 being exploited?

CVE-2026-12413 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-12413 affect?

CVE-2026-12413 affects libreswan. Severity is high (CVSS 7.5). 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 st

How urgent is CVE-2026-12413?

Priority 43/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-50721 HIGH 8.1 UPGRADE Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of
CVE-2026-50722 HIGH 8.1 UPGRADE Libreswan, via the function RSA_authenticate_hash_signature_pkcs1_1_5_rsa(), did not correctly verify the DER

References

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