OCSP responder certificate validity period not checked in public_key

{
  "id": "38a22ca90ea71e1d8c94071f8abc78c09d244e6ccfc412f9c605a89664bd8643",
  "url": "https://osv.dev/vulnerability/CVE-2026-42791",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "OCSP responder certificate validity period not checked in public_key",
    "summary": "Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_ocsp module) allows forged OCSP responses signed with an expired responder certificate to be accepted as valid. OCSP response verification in pubkey_ocsp:verify_response/5 and pubkey_ocsp:is_authorized_responder/3 in lib/public_key/src/pubkey_ocsp.erl does not check the validity period (notBefore/notAfter) of the OCSP responder certificate. An attacker who has obtained the private key of an expired CA-designated OCSP responder certificate can forge OCSP responses that Erlang/OTP accepts as valid. This affects TLS clients using OCSP stapling via the ssl application: a malicious or compromised server can present a revoked TLS certificate together with a forged OCSP response signed by an expired responder key, and the client will accept the revoked certificate as valid. It also affects applications calling public_key:pkix_ocsp_validate/5 directly, where the impact depends on the use case — server-side client certificate validation using this API may allow authentication bypass with a revoked client certificate. This issue affects OTP from OTP 27.0 before OTP 29.0.1, OTP 28.5.0.1 and OTP 27.3.4.12, corresponding to public_key from 1.16 before 1.21.1, 1.20.3.1 and 1.17.1.3.",
    "evidence": "osv:CVE-2026-42791",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-42791",
      "aliases": [
        "CVE-2026-42791",
        "EEF-CVE-2026-42791",
        "GHSA-cjxj-wj6x-3fff"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/erlang/otp",
              "type": "GIT",
              "events": [
                {
                  "introduced": "601a012837ea0a5c8095bf24223132824177124d"
                },
                {
                  "fixed": "a2394acad3e3b8fa74d40905cb79bac2ab68258a"
                },
                {
                  "introduced": "9e6f6742c4d9e9915ee8af0dcb7d97cf1f836116"
                },
                {
                  "fixed": "5770157eabdd4e8b0b83d64fd8b207c0150c2b64"
                },
                {
                  "introduced": "550d7b7898706c7822362c42e7b93120c1d1f29a"
                },
                {
                  "fixed": "f26c7e590c5d1b3afa0dee38093442df117822e3"
                },
                {
                  "fixed": "7995f1fdaee3da569bb810358ce0f546471d169b"
                },
                {
                  "fixed": "b3870e02405c709a872b01ba6086065620cdfe76"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "27.0"
                      },
                      {
                        "fixed": "27.3.4.12"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "28.0"
                      },
                      {
                        "fixed": "28.5.0.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "29.0"
                      },
                      {
                        "fixed": "29.0.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "7995f1fdaee3da569bb810358ce0f546471d169b"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "b3870e02405c709a872b01ba6086065620cdfe76"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "patch-base-27",
            "OTP-27.3.4",
            "patch-base-28",
            "OTP-28.5",
            "OTP-29.0",
            "OTP-27.3.4.9",
            "OTP-27.3.4.10",
            "OTP-28.4",
            "OTP-27.0",
            "OTP-27.3.4.11",
            "OTP-28.0",
            "OTP-27.3.4.8",
            "OTP-27.3.4.6",
            "OTP-27.3.4.7",
            "OTP-27.3",
            "OTP-27.3.4.5",
            "OTP-27.3.4.4",
            "OTP-28.1",
            "OTP-27.3.4.3",
            "OTP-27.3.3",
            "OTP-27.3.4.2",
            "OTP-27.3.4.1",
            "OTP-27.3.2",
            "OTP-27.2",
            "OTP-27.3.1",
            "OTP-27.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-42791.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:25.489396680Z",
      "provider": "osv",
      "references": [
        "https://cna.erlef.org/cves/CVE-2026-42791.html",
        "https://github.com",
        "https://osv.dev/vulnerability/EEF-CVE-2026-42791",
        "https://www.erlang.org/doc/system/versions.html#order-of-versions",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42791.json",
        "https://github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-42791",
        "https://github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b",
        "https://github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76",
        "https://github.com/erlang/otp"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-295",
          "CWE-672"
        ],
        "cna_assigner": "EEF",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "1.16"
                  },
                  {
                    "fixed": "1.17.1.3"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "ChangesAt"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42791.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-42791",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 491958,
  "published_at": "2026-05-27T12:23:13.584+00:00"
}