Input validation error in libreswan - CVE-2026-50721

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Main Vulnerability Database Vulnerabilities #VU135209

Input validation error in libreswan - CVE-2026-50721

Published: June 25, 2026


Vulnerability identifier: #VU135209
CSH Severity: Medium
CVSS v4: 8.7 [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]
CVE-ID: CVE-2026-50721
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

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.


Affected software

libreswan
Anolis OS
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
openEuler
Red Hat Enterprise Linux Fast Datapath
libreswan (Red Hat package)
libreswan
libreswan-debuginfo
libreswan-help
libreswan-debugsource
libreswan-doc

How to mitigate CVE-2026-50721

Install security update from vendor's website.

libreswan - update to 5.3.1
libreswan (Red Hat package) - addressed in versions 4.12-2.el8_10.6, 4.15-10.el9_8, 5.3.2-1.el9fdp, 5.3.2-1.el10_2
libreswan - addressed in versions 4.12-2.0.2, 5.1-2
libreswan-debuginfo - update to 4.15-3
libreswan-help - update to 4.15-3
libreswan-debugsource - update to 4.15-3
libreswan - update to 4.15-3
libreswan-doc - update to 5.1-2

External References

Related Security Bulletins