Authen::SASL::Perl::DIGEST_MD5 versions before 2.2100 for Perl accept replayed authentication responses via unverified nonce in server_step

{
  "id": "78895fa4bf00d4cbc1bc0569f90e4ce0651fc0c8a3bbbb68b6ce6dbda4dd046d",
  "url": "https://osv.dev/vulnerability/CVE-2026-86219",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Authen::SASL::Perl::DIGEST_MD5 versions before 2.2100 for Perl accept replayed authentication responses via unverified nonce in server_step",
    "summary": "Authen::SASL::Perl::DIGEST_MD5 versions before 2.2100 for Perl accept replayed authentication responses via unverified nonce in server_step. server_start generates a fresh nonce and sends it in the challenge, and nothing later compares that value against the nonce the client returns. server_step derives the expected digest from the client's own parameters, so a response verifies whenever its digest matches the nonce it carries. The count table it also checks is keyed on the client-supplied nonce and starts empty in each new server object, so a captured first response, carrying `nc=00000001`, passes that too. RFC 2831 defines the nonce in the response as the value the server sent in the preceding challenge. An attacker who observes one successful `qop=auth` exchange can replay the captured response against a later session for the same service, host, realm and user, and authenticate as that user without knowing the password.",
    "evidence": "osv:CVE-2026-86219",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-86219",
      "aliases": [
        "CVE-2026-86219"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/perl-authen-sasl/perl-authen-sasl",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "57a740d54087fa822d8660a0c7d823ca5b1217ae"
                },
                {
                  "fixed": "94337367030612842924f697cead29964a96448d"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "2.2100"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "94337367030612842924f697cead29964a96448d"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v2.2000",
            "v2.1900",
            "v2.1800",
            "v2.1700",
            "v2.16",
            "v2.15",
            "v2.14",
            "v2.13",
            "v2.12",
            "v2.11"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-86219.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:26.272490548Z",
      "provider": "osv",
      "references": [
        "https://cpan.org/modules",
        "https://datatracker.ietf.org/doc/html/rfc2831#section-2.1.2",
        "https://metacpan.org/release/EHUELS/Authen-SASL-2.2000/source/lib/Authen/SASL/Perl/DIGEST_MD5.pm#L203-222",
        "https://metacpan.org/release/EHUELS/Authen-SASL-2.2000/source/lib/Authen/SASL/Perl/DIGEST_MD5.pm#L410-414",
        "https://www.cve.org/CVERecord?id=CVE-2025-40918",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86219.json",
        "https://metacpan.org/release/EHUELS/Authen-SASL-2.2100/changes",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-86219",
        "https://github.com/perl-authen-sasl/perl-authen-sasl/commit/94337367030612842924f697cead29964a96448d.patch",
        "https://github.com/perl-authen-sasl/perl-authen-sasl"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-294"
        ],
        "cna_assigner": "CPANSec",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86219.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-86219",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 492966,
  "published_at": "2026-09-06T17:46:30.34+00:00"
}