MediumFix available
erlang — security advisory
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.
- Products
- erlang
- Affected versions
- 1:27.3+dfsg-1ubuntu1, 1:27.3+dfsg-1ubuntu1.1, 1:27.3.4.1+dfsg-1, 1:27.3.4.1+dfsg-1build1, 1:27.3.4.1+dfsg-1ubuntu0.1, 1:27.3.4.3+dfsg-1, 1:27.3.4.4+dfsg-1, 1:27.3.4.6+dfsg-1, 1:27.3.4.6+dfsg-1ubuntu0.1
- Fixed versions
- 1:27.3.4.6+dfsg-1ubuntu0.2
- CVEs
- CVE-2026-42791
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 28 Oct 2026, 10:04 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-42791
erlang
Fixed versions: Not specified
erlang
Fixed versions: 1:27.3.4.6+dfsg-1ubuntu0.2
Complete source record
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"availability": "No subscription required"
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],
"modified": "2026-10-08T19:47:10.138142198Z",
"provider": "osv",
"upstream": [
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],
"references": [
"https://ubuntu.com/security/CVE-2026-42791",
"https://www.cve.org/CVERecord?id=CVE-2026-42791",
"https://github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff",
"https://cna.erlef.org/cves/CVE-2026-42791.html",
"https://osv.dev/vulnerability/EEF-CVE-2026-42791",
"https://github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b",
"https://github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76",
"https://www.erlang.org/doc/system/versions.html#order-of-versions",
"https://ubuntu.com/security/notices/USN-8901-1"
]
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"related_cves": [
{
"value": "CVE-2026-42791",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 104544,
"published_at": "2026-05-27T14:16:00+00:00"
}