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PatchSiren cyber security CVE debrief

CVE-2026-50722 The Libreswan Project CVE debrief

CVE-2026-50722 is a high-severity vulnerability in Libreswan, a popular open-source VPN software. The vulnerability arises from improper verification of DER ASN.1 encoding in the IKEv2 AUTH payload, allowing remote attackers to forge AUTH payloads and impersonate legitimate users when small public exponents are used. Additionally, attackers can trigger a denial-of-service condition by encoding a shorter than expected hash in the AUTH payload, causing the daemon to abort and restart. The vulnerability has a CVSS score of 8.1 and is classified as HIGH severity.

Vendor
The Libreswan Project
Product
libreswan
CVSS
HIGH 8.1
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-02
Original CVE updated
2026-07-07
Advisory published
2026-07-02
Advisory updated
2026-07-07

Who should care

Organizations using Libreswan for VPN connections should prioritize patching this vulnerability to prevent potential impersonation and denial-of-service attacks. The vulnerability can be exploited remotely, and its high severity score indicates a significant risk to affected systems.

Technical summary

The vulnerability is caused by the RSA_authenticate_hash_signature_pkcs1_1_5_rsa() function in Libreswan not correctly verifying the DER encoding of the ASN.1 digest when the IKEv2 AUTH payload is encoded using RSASSA-PKCS1-v1_5 (RFC 8017). This allows remote attackers to forge AUTH payloads and impersonate legitimate users when small public exponents are used (e.g., e=3). Furthermore, encoding a shorter than expected hash in the AUTH payload can trigger an assertion, leading to a denial-of-service condition. The daemon aborts and restarts upon exploitation, and continued exploitation can cause sustained denial of service. Remote code execution is not possible, and X.509 certificate verifications of the remote IKE peer are not affected.

Defensive priority

High

Recommended defensive actions

  • Apply patches or updates provided by Libreswan to address CVE-2026-50722
  • Review and update VPN configurations to ensure secure key exchange and authentication
  • Monitor VPN connections for suspicious activity and implement additional logging and monitoring measures
  • Consider implementing compensating controls, such as network segmentation and access controls, to limit the impact of potential attacks
  • Review asset inventory to identify systems using Libreswan and prioritize patching
  • Track changes and updates to Libreswan and related systems for CVE-2026-50722
  • Verify that VPN configurations are up-to-date and align with current security guidelines

Evidence notes

The CVE record was published on 2026-07-02T22:16:43.550Z and was last modified on 2026-07-07T18:16:39.300Z. The NVD entry is currently Undergoing Analysis. The vulnerability is related to CWE-347 and CWE-617.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-02T22:16:43.550Z and has not been modified since then. The NVD entry is currently Undergoing Analysis.