CVE-2026-42791 (GCVE-0-2026-42791)

Vulnerability from cvelistv5 – Published: 2026-05-27 12:23 – Updated: 2026-05-27 15:41
VLAI
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 27.3.4.12, 28.5.0.1, and 29.0.1 corresponding to public_key from 1.16 before 1.17.1.3, 1.20.3.1, and 1.21.1.
Severity
6.3 (Medium)
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
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-295 - Improper Certificate Validation
  • CWE-672 - Operation on a Resource after Expiration or Release
Assigner
EEF
References
Impacted products
Vendor Product Version
Erlang OTP Affected: 1.16 , < * (otp)
    cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
 Create a notification for this product.
Erlang OTP Affected: 27.0 , < * (otp)
Affected: 2b1a742c651b90f8a7a1fb2ddde73f29915ea376 , < * (git)
    cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Jakub Witczak Ingela Anderton Andin
Show details on NVD website
To clipboard 

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    "vulnrichment": {
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Validation\"}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"version\": \"4.0\", \"baseScore\": 6.3, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"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\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"HIGH\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"LOW\", \"vulnIntegrityImpact\": \"LOW\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"LOW\", \"vulnConfidentialityImpact\": \"NONE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"cpes\": [\"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/erlang/otp\", \"vendor\": \"Erlang\", \"modules\": [\"pubkey_ocsp\"], \"product\": \"OTP\", \"versions\": [{\"status\": \"affected\", \"changes\": [{\"at\": \"1.17.1.3\", \"status\": \"unaffected\"}, {\"at\": \"1.20.3.1\", \"status\": \"unaffected\"}, {\"at\": \"1.21.1\", \"status\": \"unaffected\"}], \"version\": \"1.16\", \"lessThan\": \"*\", \"versionType\": \"otp\"}], \"packageURL\": \"pkg:otp/public_key?repository_url=https:%2F%2Fgithub.com%2Ferlang%2Fotp\u0026vcs_url=git%20https:%2F%2Fgithub.com%2Ferlang%2Fotp.git\", \"packageName\": \"public_key\", \"programFiles\": [\"src/pubkey_ocsp.erl\"], \"defaultStatus\": \"unknown\", \"programRoutines\": [{\"name\": \"pubkey_ocsp:verify_response/5\"}, {\"name\": \"pubkey_ocsp:is_authorized_responder/3\"}]}, {\"cpes\": [\"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/erlang/otp\", \"vendor\": \"Erlang\", \"modules\": [\"pubkey_ocsp\"], \"product\": \"OTP\", \"versions\": [{\"status\": \"affected\", \"changes\": [{\"at\": \"27.3.4.12\", \"status\": \"unaffected\"}, {\"at\": \"28.5.0.1\", \"status\": \"unaffected\"}, {\"at\": \"29.0.1\", \"status\": \"unaffected\"}], \"version\": \"27.0\", \"lessThan\": \"*\", \"versionType\": \"otp\"}, {\"status\": \"affected\", \"changes\": [{\"at\": \"7995f1fdaee3da569bb810358ce0f546471d169b\", \"status\": \"unaffected\"}, {\"at\": \"b3870e02405c709a872b01ba6086065620cdfe76\", \"status\": \"unaffected\"}], \"version\": \"2b1a742c651b90f8a7a1fb2ddde73f29915ea376\", \"lessThan\": \"*\", \"versionType\": \"git\"}], \"packageURL\": \"pkg:github/erlang/otp\", \"packageName\": \"erlang/otp\", \"programFiles\": [\"lib/public_key/src/pubkey_ocsp.erl\"], \"collectionURL\": \"https://github.com\", \"defaultStatus\": \"unknown\", \"programRoutines\": [{\"name\": \"pubkey_ocsp:verify_response/5\"}, {\"name\": \"pubkey_ocsp:is_authorized_responder/3\"}]}], \"references\": [{\"url\": \"https://github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff\", \"tags\": [\"vendor-advisory\", \"related\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-42791.html\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-42791\", \"tags\": [\"related\"]}, {\"url\": \"https://www.erlang.org/doc/system/versions.html#order-of-versions\", \"tags\": [\"x_version-scheme\"]}, {\"url\": \"https://github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76\", \"tags\": [\"patch\"]}], \"workarounds\": [{\"lang\": \"en\", \"value\": \"* For TLS clients using the ssl application, disable OCSP stapling by setting {stapling, no_staple} in the client options, or switch to CRL-based revocation checking with {crl_check, true}.\\n* For applications calling public_key:pkix_ocsp_validate/5 directly, validate the responder certificate\u0027s validity period in application code before calling the function.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cul\u003e\u003cli\u003eFor TLS clients using the \u003ctt\u003essl\u003c/tt\u003e application, disable OCSP stapling by setting \u003ctt\u003e{stapling, no_staple}\u003c/tt\u003e in the client options, or switch to CRL-based revocation checking with \u003ctt\u003e{crl_check, true}\u003c/tt\u003e.\u003c/li\u003e\u003cli\u003eFor applications calling \u003ctt\u003epublic_key:pkix_ocsp_validate/5\u003c/tt\u003e directly, validate the responder certificate\u0027s validity period in application code before calling the function.\u003c/li\u003e\u003c/ul\u003e\", \"base64\": false}]}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"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.\\n\\nOCSP 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.\\n\\nThis 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 \\u2014 server-side client certificate validation using this API may allow authentication bypass with a revoked client certificate.\\n\\nThis issue affects OTP from OTP 27.0 before OTP 27.3.4.12, 28.5.0.1, and 29.0.1 corresponding to public_key from 1.16 before 1.17.1.3, 1.20.3.1, and 1.21.1.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"Improper Certificate Validation vulnerability in Erlang OTP \u003ctt\u003epublic_key\u003c/tt\u003e (\u003ctt\u003epubkey_ocsp\u003c/tt\u003e module) allows forged OCSP responses signed with an expired responder certificate to be accepted as valid.\u003cp\u003eOCSP response verification in \u003ctt\u003epubkey_ocsp:verify_response/5\u003c/tt\u003e and \u003ctt\u003epubkey_ocsp:is_authorized_responder/3\u003c/tt\u003e in \u003ctt\u003elib/public_key/src/pubkey_ocsp.erl\u003c/tt\u003e does not check the validity period (\u003ctt\u003enotBefore\u003c/tt\u003e/\u003ctt\u003enotAfter\u003c/tt\u003e) 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.\u003c/p\u003e\u003cp\u003eThis affects TLS clients using OCSP stapling via the \u003ctt\u003essl\u003c/tt\u003e 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 \u003ctt\u003epublic_key:pkix_ocsp_validate/5\u003c/tt\u003e directly, where the impact depends on the use case \\u2014 server-side client certificate validation using this API may allow authentication bypass with a revoked client certificate.\u003c/p\u003e\u003cp\u003eThis issue affects OTP from OTP 27.0 before OTP 27.3.4.12, 28.5.0.1, and 29.0.1 corresponding to \u003ctt\u003epublic_key\u003c/tt\u003e from 1.16 before 1.17.1.3, 1.20.3.1, and 1.21.1.\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-295\", \"description\": \"CWE-295 Improper Certificate Validation\"}, {\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-672\", \"description\": \"CWE-672 Operation on a Resource after Expiration or Release\"}]}], \"configurations\": [{\"lang\": \"en\", \"value\": \"For the ssl application, OCSP stapling must be enabled by setting the stapling option to staple in the TLS client options. OCSP stapling is not enabled by default.\\n\\nApplications calling public_key:pkix_ocsp_validate/5 directly are unconditionally affected when that function is used.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"For the \u003ctt\u003essl\u003c/tt\u003e application, OCSP stapling must be enabled by setting the \u003ctt\u003estapling\u003c/tt\u003e option to \u003ctt\u003estaple\u003c/tt\u003e in the TLS client options. OCSP stapling is not enabled by default.\u003cp\u003eApplications calling \u003ctt\u003epublic_key:pkix_ocsp_validate/5\u003c/tt\u003e directly are unconditionally affected when that function is used.\u003c/p\u003e\", \"base64\": false}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"27.3.4.12\", \"versionStartIncluding\": \"27.0\"}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"28.5.0.1\", \"versionStartIncluding\": \"28.0\"}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"29.0.1\", \"versionStartIncluding\": \"29.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-05-27T15:41:07.758Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-42791\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-27T15:41:07.758Z\", \"dateReserved\": \"2026-04-29T18:06:33.251Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-05-27T12:23:13.584Z\", \"assignerShortName\": \"EEF\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.