Is CVE-2026-50721 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-50721 being exploited in the wild.

How severe is CVE-2026-50721?

High severity, with a CVSS score of 8.1, published 2 July 2026.

Which products and versions are affected?

The Libreswan Project Libreswan versions up to and including 5.3.

Is there a fix for CVE-2026-50721?

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-2026-50721 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-50721?

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.

CVE-2026-50721: Libreswan improper signature verification in IKEv1 RSA authentication

CVE-2026-50721 · Severity: high · CVSS 8.1 · Published 2026-07-02

Libreswan, a tool used to create secure VPN connections, contains a vulnerability in how it handles certain encrypted authentication messages. An attacker could exploit this to crash the VPN service, causing a denial of service, or potentially bypass authentication if the system uses older, weak security keys. This could allow unauthorized access to the network or disrupt secure communications for all users.

Technologies: The Libreswan Project Libreswan. Vendors: The Libreswan Project.

Quick answers

Is CVE-2026-50721 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-50721 being exploited in the wild.
How severe is CVE-2026-50721?: High severity, with a CVSS score of 8.1, published 2 July 2026.
Which products and versions are affected?: The Libreswan Project Libreswan versions up to and including 5.3.
Is there a fix for CVE-2026-50721?: 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-2026-50721 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-50721?: 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 Libreswan's RSA_authenticate_hash_signature_raw_rsa() function due to improper verification of the authentication hash length in IKEv1 SIG payloads (RFC 2313). A remote, unauthenticated attacker can trigger a reachable assertion by providing a shorter-than-expected hash, resulting in a daemon crash and sustained denial-of-service upon repeated exploitation. Furthermore, if small public exponents (e.g., e=3) are utilized, a variation of the Bleichenbacher attack can be employed to forge signatures and bypass authentication. This issue is specific to IKEv1 RSA-SHA1 authentication and does not affect X.509 certificate verifications. The vulnerability is addressed in version 5.3.1.

Affected products

The Libreswan Project libreswan versions up to and including 5.3

Timeline

2026-03-24: disclosed: Vulnerability reported to Libreswan Project
2026-06-16: other: Advanced notice provided to customers and distributions
2026-06-24: patched: Public announcement and release of version 5.3.1
2026-07-02: advisory: NVD publication date

References

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