Input validation error in libreswan - CVE-2026-50721
Published: June 25, 2026
Vulnerability identifier: #VU135209
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-50721
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: libreswan.org
Affected software:
libreswan
libreswan
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper input validation in RSA_authenticate_hash_signature_raw_rsa() when processing an invalidly formatted PKCS#1 v1.5 RSA signature in an IKEv1 SIG payload. A remote attacker can send a specially crafted IKEv1 packet with a shorter than expected hash to cause a denial of service.
The issue affects IKEv1 RSA-SHA1 authentication payload handling and can trigger an assertion that causes libreswan to abort and restart.
How to mitigate CVE-2026-50721
Install security update from vendor's website.