CVE-2026-50721: libreswan before 5.3.1 (exclusive), 0 through 5.3

Affected technology

libreswan · before 5.3.1 (exclusive)
libreswan

libreswan · 0 through 5.3
The Libreswan Project

Component: Not specified by the source
Function: RSA_authenticate_hash_signature_raw_rsa

Attack conditions (Source advisory, CVSS 3.1): Network (remote) · No privileges required · No user interaction required

Attack conditions (NVD, CVSS 3.1): Network (remote) · No privileges required · No user interaction required

What an attacker can do

A remote attacker can use a variation on the Bleichenbacher attack to forge the SIG payload when small public exponents are being used (e.g., e=3), which could lead to impersonation. Source advisory’s CVSS 3.1 assessment (base score 8.1/10) rates confidentiality, integrity and availability impact as high. NVD’s CVSS 3.1 assessment (base score 5.9/10) rates confidentiality and integrity impact as none; availability impact as high.