Net::SAML2 versions before 0.86 for Perl allow SAML authentication bypass by verifying responses against the response-embedded certificate in verify_xml when no trust anchor is configured

{
  "id": "1847af062e85dd3a314a18d1ca3a46f27418643e7817dae103e0fd226534ea8f",
  "url": "https://osv.dev/vulnerability/CVE-2026-18089",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Net::SAML2 versions before 0.86 for Perl allow SAML authentication bypass by verifying responses against the response-embedded certificate in verify_xml when no trust anchor is configured",
    "summary": "Net::SAML2 versions before 0.86 for Perl allow SAML authentication bypass by verifying responses against the response-embedded certificate in verify_xml when no trust anchor is configured. verify_xml in Net::SAML2::Role::VerifyXML runs \"return if !$anchors && !$cacert;\" as soon as the XML::Sig check succeeds, and that check uses the X.509 certificate taken from the response's own dsig:KeyInfo/dsig:X509Certificate element, so an unanchored response is checked only against the key it carries. Binding::POST declares cacert as an optional Maybe[Str] with no default, so a POST binding built without one takes that path, and _verify_encrypted_assertion returns early the same way with \"return $xml unless $cacert;\". Any caller that constructs Binding::POST or calls Assertion->new_from_xml without a cacert, cert_text, or anchors argument accepts a response signed by an attacker generated key whose self-signed certificate is embedded in that response, authenticating an arbitrary assertion.",
    "evidence": "osv:CVE-2026-18089",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-18089",
      "aliases": [
        "CVE-2026-18089"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/perl-net-saml2/perl-net-saml2",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "b679659178e278a4a53fe88d9eb58461a6e78b13"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "0.86"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  }
                ]
              }
            }
          ],
          "versions": [
            "0.85",
            "0.84",
            "0.83",
            "0.82",
            "0.81",
            "0.80",
            "0.79",
            "0.78",
            "0.77",
            "0.76",
            "0.75",
            "0.74",
            "0.73",
            "0.72",
            "0.71",
            "0.70",
            "0.69",
            "0.68",
            "0.67",
            "0.66",
            "0.65",
            "0.64",
            "0.63",
            "0.62",
            "0.61",
            "0.60",
            "0.58",
            "0.57",
            "0.56",
            "0.55",
            "0.54",
            "0.53",
            "0.52",
            "0.51",
            "0.49",
            "0.48",
            "0.47",
            "0.45",
            "0.44",
            "0.43",
            "0.42",
            "0.41",
            "0.40",
            "0.39",
            "0.38",
            "0.37-TRIAL",
            "0.36-TRIAL",
            "0.35-TRIAL",
            "0.34",
            "0.33-TRIAL",
            "0.32",
            "0.31-TRIAL",
            "0.30-TRIAL",
            "0.29",
            "v0.26-TRIAL",
            "0.25",
            "v0.20",
            "0.20",
            "0.20.03-TRIAL",
            "perl-net-saml2-0.19.05",
            "0.19.05",
            "v0.17_06",
            "v0.17",
            "v0.16",
            "v0.15",
            "v0.14",
            "v0.12",
            "v0.11",
            "v0.10"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-18089.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:22.167714656Z",
      "provider": "osv",
      "references": [
        "https://cpan.org/modules",
        "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Binding/POST.pm#L21",
        "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Protocol/Assertion.pm#L84",
        "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Role/VerifyXML.pm#L32",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/18xxx/CVE-2026-18089.json",
        "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.88/source/Changes",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-18089",
        "https://github.com/perl-net-saml2/perl-Net-SAML2"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-295",
          "CWE-347"
        ],
        "cna_assigner": "CPANSec",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/18xxx/CVE-2026-18089.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-18089",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 488386,
  "published_at": "2026-08-03T12:42:08.879+00:00"
}