# CVE-2026-12413: Libreswan pluto daemon denial of service in IKEv2 fragmentation

Source: https://junglewise.ai/threats/cve-2026-12413-libreswan-pluto-daemon-denial-of-service-in-ikev2-fragmentation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-02. Updated: 2026-07-02  
License: CC BY 4.0 with a link back

CVE-2026-12413 · Severity: high · CVSS 7.5 · Published 2026-07-02

Libreswan is a widely used tool for creating secure VPN connections. A flaw in how it handles specific types of encrypted network traffic (IKEv2 fragments) allows a remote attacker to crash the service. If an attacker repeatedly sends these malformed messages, they can cause a sustained denial of service, preventing users from connecting to the VPN.

Technologies: [The Libreswan Project Libreswan](https://junglewise.ai/threats/technologies/libreswan). Vendors: [The Libreswan Project](https://junglewise.ai/threats/vendors/the-libreswan-project).

## Quick answers

**Is CVE-2026-12413 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-12413 being exploited in the wild.

**How severe is CVE-2026-12413?** High severity, with a CVSS score of 7.5, published 2 July 2026.

**Which products and versions are affected?** The Libreswan Project Libreswan 4.6 to 5.3.

**Is there a fix for CVE-2026-12413?** A patch was published on 2026-06-24: Public announcement and release of version 5.3.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-12413 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-12413?** Check whether you run The Libreswan Project Libreswan at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in the Libreswan pluto daemon within the reassemble_v2_incoming_fragments() function. The function fails to properly validate the number of unknown outer payloads before storing them in the fixed-size msg_digest.digest[PAYLIMIT] array. An off-by-one error in a PASSERT check (using < instead of <=) causes the daemon to abort and restart when processing specifically malformed IKEv2 fragments. This is a remote, unauthenticated denial-of-service vulnerability; however, remote code execution is not possible. The issue is resolved in version 5.3.1.

## Affected products

- The Libreswan Project libreswan 4.6 to 5.3

## Timeline

- 2026-06-16: disclosed: Libreswan notified of the issue
- 2026-06-24: patched: Public announcement and release of version 5.3.1
- 2026-07-02: advisory: NVD publication date

## References

- [https://libreswan.org/security/CVE-2026-12413/](https://libreswan.org/security/CVE-2026-12413/)
- [https://libreswan.org/security/CVE-2026-12413/CVE-2026-12413.txt](https://libreswan.org/security/CVE-2026-12413/CVE-2026-12413.txt)

## Related threats

- [Libreswan improper signature verification in IKEv1 RSA authentication](https://junglewise.ai/threats/cve-2026-50721-libreswan-improper-signature-verification-in-ikev1-rsa)