OCSP responder certificate validity period not checked in public_key
Summary
| CVE | CVE-2026-42791 |
|---|---|
| State | PUBLISHED |
| Assigner | EEF |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-27 14:16:53 UTC |
| Updated | 2026-05-27 19:38:46 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 6.3 MEDIUM from 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.000590000 probability, percentile 0.186170000 (date 2026-06-01)
Problem Types: CWE-295 | CWE-672 | CWE-295 CWE-295 Improper Certificate Validation | CWE-672 CWE-672 Operation on a Resource after Expiration or Release
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | Secondary | 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/E:X/C... |
| 4.0 | CNA | CVSS | 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 |
CVSS v4.0 Breakdown
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| cna.erlef.org/cves/CVE-2026-42791.html | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | cna.erlef.org | |
| github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| osv.dev/vulnerability/EEF-CVE-2026-42791 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | osv.dev | |
| github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| www.erlang.org/doc/system/versions.html | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | www.erlang.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Jakub Witczak (en)
CNA: Ingela Anderton Andin (en)
Additional Advisory Data
Workarounds
CNA: * 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}. * For applications calling public_key:pkix_ocsp_validate/5 directly, validate the responder certificate's validity period in application code before calling the function.