Improper Verification of Cryptographic Signature Affecting libreswan/libreswan package, versions [,5.3.1)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-UNMANAGED-LIBRESWANLIBRESWAN-17807925
- published3 Jul 2026
- disclosed3 Jul 2026
- creditUnknown
Introduced: 3 Jul 2026
CVE-2026-50721 (opens in a new tab)How to fix?
Upgrade libreswan/libreswan to version 5.3.1 or higher.
Overview
Affected versions of this package are vulnerable to Improper Verification of Cryptographic Signature in the RSA_authenticate_hash_signature_raw_rsa function. An attacker can cause the daemon to abort and restart by sending a specially crafted IKEv1 packet with a SIG payload encoded using PKCS #1 RSA Encryption, where the authentication hash is shorter than expected. Continued exploitation can result in sustained service disruption.
Workaround
This vulnerability can be mitigated by migrating IKEv1 connections to IKEv2 where authby=ecdsa or authby=rsa-sha2 can be configured, or by changing authentication to use PSK via authby=secret for static tunnel configurations after coordination with the remote peer.