{"id":"UBUNTU-CVE-2026-50721","details":"Libreswan, 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.","modified":"2026-07-11T00:15:15.283507816Z","published":"2026-07-02T22:16:00Z","upstream":["CVE-2026-50721"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-50721"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-50721"},{"type":"REPORT","url":"https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt"},{"type":"REPORT","url":"https://libreswan.org/security/CVE-2026-50721/"},{"type":"REPORT","url":"https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt"},{"type":"REPORT","url":"https://www.rfc-editor.org/rfc/rfc2313"}],"affected":[{"package":{"name":"libreswan","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/libreswan?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.20-7build1","3.21-2","3.22-1","3.22-2","3.22-3","3.22-4","3.23-1","3.23-4"],"ecosystem_specific":{"binaries":[{"binary_version":"3.23-4","binary_name":"libreswan"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50721.json"}},{"package":{"name":"libreswan","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/libreswan?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.29-2","3.29-2build1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.29-2build1","binary_name":"libreswan"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50721.json"}},{"package":{"name":"libreswan","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/libreswan?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.32-3ubuntu3"],"ecosystem_specific":{"binaries":[{"binary_version":"3.32-3ubuntu3","binary_name":"libreswan"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50721.json"}},{"package":{"name":"libreswan","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/libreswan?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.11-1ubuntu1","4.12-1ubuntu1","4.14-1ubuntu1","4.14-1ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_name":"libreswan","binary_version":"4.14-1ubuntu2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50721.json"}},{"package":{"name":"libreswan","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/libreswan?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.14-1ubuntu2","5.2-2.2ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"libreswan","binary_version":"5.2-2.2ubuntu1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50721.json"}},{"package":{"name":"libreswan","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/libreswan?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.2-2.2ubuntu1","5.2-2.2ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_name":"libreswan","binary_version":"5.2-2.2ubuntu2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50721.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"medium"}]}