Security advisory

{
  "id": "17125e0596985b3a251261b86c1821ab5a29e45c8bcabce55fc785424166c13c",
  "url": "https://osv.dev/vulnerability/CVE-2026-50721",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2026-50721",
    "summary": "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.",
    "evidence": "osv:CVE-2026-50721",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-50721",
      "aliases": [
        "CVE-2026-50721"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/libreswan/libreswan",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "de24519eb4ff49803a21d75e880c87834cf33beb"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:libreswan:libreswan:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "5.3.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v5.3",
            "v5.2",
            "v5.1",
            "v5.0rc2",
            "v5.0rc1",
            "v4.9",
            "v4.8",
            "v4.7",
            "v4.6",
            "v4.5",
            "v4.4",
            "v4.3",
            "v4.2",
            "v4.1",
            "v4.0",
            "v3.30",
            "v3.28",
            "v3.27",
            "v3.26",
            "v3.25",
            "v3.22",
            "v3.22dr1",
            "v3.21",
            "v3.20",
            "v3.21rc5",
            "v3.20dr4",
            "v3.20dr3",
            "v3.19",
            "v3.18",
            "v3.18dr2",
            "v3.16",
            "v3.17",
            "v3.16rc3",
            "v3.16rc2",
            "v3.14",
            "v3.14rc3",
            "v3.14rc2",
            "v3.7",
            "v3.6",
            "v3.5",
            "v3.4",
            "v3.3",
            "v3.1",
            "v3.11dr1",
            "v3.2rc1",
            "v2.93",
            "v2.92",
            "libreswan-0.0.1",
            "0.9.9",
            "v2.6.38",
            "v2.6.38rc2",
            "v2.6.38rc1",
            "v2.6.38dr2",
            "v2.6.32",
            "v2.6.37",
            "v2.6.36",
            "v2.6.36rc1",
            "v2.6.36dr1",
            "v2.6.35dr1",
            "v2.6.34",
            "v2.6.34rc6",
            "v2.6.34rc5",
            "v2.6.34rc2",
            "v2.6.34rc1",
            "v2.6.34dr2",
            "v2.6.34dr1",
            "v2.6.33rc1",
            "v2.6.33dr2",
            "v2.6.32rc9",
            "v2.6.32rc8",
            "v2.6.32rc7",
            "v2.6.32rc6",
            "v2.6.32rc5",
            "v2.6.32rc3",
            "v2.6.32rc1",
            "v2.6.32dr5",
            "v2.6.32dr4",
            "v2.6.32dr3",
            "v2.6.32dr1",
            "v2.6.29rc2",
            "v2.6.29",
            "v2.6.28dr1",
            "v2.6.27dr1",
            "v2.6.26",
            "v2.6.26rc1",
            "v2.6.24",
            "v2.6.24rc5",
            "v2.6.24rc4",
            "v2.6.24rc3",
            "v2.6.24rc2",
            "v2.6.23",
            "v2.6.23dr1",
            "v2.6.22dr1",
            "v2.6.21",
            "v2.6.20bis",
            "v2.6.20rc2",
            "v2.6.20",
            "v2.6.19",
            "v2.6.18",
            "v2.6.18rc1",
            "v2.6.16",
            "v2.6.16dr5",
            "v2.6.16dr4",
            "v2.6.16dr3",
            "v2.6.16dr2",
            "v2.6.16dr1",
            "v2.6.15",
            "v2.6.15dr2",
            "v2.6.14",
            "v2.6.07",
            "v2.6.03",
            "v2.6.01",
            "v2.5.03",
            "v2.5.01",
            "pre_FreeBSD_merge_200607"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-50721.json"
          }
        }
      ],
      "modified": "2026-10-27T02:30:30.130290243Z",
      "provider": "osv",
      "references": [
        "https://libreswan.org/security/CVE-2026-50721/",
        "https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt",
        "https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt",
        "https://www.rfc-editor.org/rfc/rfc2313"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2026-50721",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 460021,
  "published_at": "2026-07-02T22:16:43.367+00:00"
}