SecuriTricks - CVE-2026-42791

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.

Product(s) Impacted

Vendor	Product	Versions
Erlang	Otp Public Key	27.0-27.3.4.12 1.16-1.17.1.3, 1.20.3.1, 1.21.1

Weaknesses

Common security weaknesses mapped to this vulnerability.

CWE-295

Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate.

*CPE(s)

Affected systems and software identified for this CVE.

Type	Vendor	Product	Version	Update	Edition	Language	Software Edition	Target Software	Target Hardware	Other Information
a	erlang	otp	27.0-27.3.4.12	/	/	/	/	/	/	/
a	erlang	public_key	1.16-1.17.1.3	/	/	/	/	/	/	/
a	erlang	public_key	1.20.3.1	/	/	/	/	/	/	/
a	erlang	public_key	1.21.1	/	/	/	/	/	/	/

References

https://cna.erlef.org/cves/CVE-2026-42791.html

https://github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b

https://github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76

https://github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff

https://osv.dev/vulnerability/EEF-CVE-2026-42791

https://www.erlang.org/doc/system/versions.html#order-of-versions

CVSS Score

6.3 / 10

CVSS Data - 4.0

Attack Vector: NETWORK
Attack Complexity: HIGH
Attack Requirements: PRESENT
Privileges Required: NONE
User Interaction: NONE
Scope:
Confidentiality Impact: NONE
Integrity Impact: LOW
Availability Impact: NONE
Exploit Maturity: NOT_DEFINED

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

View Vector String

Timeline

Published: May 27, 2026, 2:16 p.m.
Last Modified: May 27, 2026, 7:38 p.m.

Status : Undergoing Analysis

CVE has been recently published to the CVE List and has been received by the NVD.

More info

Source

6b3ad84c-e1a6-4bf7-a703-f496b71e49db

CVE-2026-42791