CVE-2026-50721

NameCVE-2026-50721
DescriptionLibreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. 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. Additionally, a remote attacker, by encoding a shorter than expected hash in the SIG payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of remote IKE peers are not affected.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
libreswan (PTS)bullseye4.3-1+deb11u4vulnerable
bullseye (security)4.3-1+deb11u3vulnerable
bookworm4.10-2+deb12u1vulnerable
trixie5.2-2.2vulnerable
forky, sid5.2-2.4vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
libreswansource(unstable)(unfixed)

Notes

https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt
Patches: https://libreswan.org/security/CVE-2026-50721/

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