CVE-2026-42791
Received
Received - Intake
Improper Certificate Validation in Erlang OTP
Publication date: 2026-05-27
Last updated on: 2026-05-27
Assigner: EEF
Description
Description
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.
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| erlang | otp | to 27.3.4.12 (exc) |
| erlang | otp | 28.5.0.1 |
| erlang | otp | 29.0.1 |
| erlang | public_key | to 1.17.1.3 (exc) |
| erlang | public_key | 1.20.3.1 |
| erlang | public_key | 1.21.1 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-672 | The product uses, accesses, or otherwise operates on a resource after that resource has been expired, released, or revoked. |
| CWE-295 | The product does not validate, or incorrectly validates, a certificate. |
Attack-Flow Graph
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