CVE-2026-42791
OCSP responder certificate validity period not checked in public_key
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.
INFO
Published Date :
May 27, 2026, 2:16 p.m.
Last Modified :
June 2, 2026, 7:18 p.m.
Remotely Exploit :
Yes !
Source :
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | LOW | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | ||||
| CVSS 4.0 | MEDIUM | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db |
Solution
- Update Erlang/OTP to a patched version.
- Apply security updates for the public_key component.
- Ensure OCSP response validation includes certificate expiry.
- Verify TLS client and server configurations.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-42791.
| URL | Resource |
|---|---|
| https://cna.erlef.org/cves/CVE-2026-42791.html | Third Party Advisory |
| https://github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b | Patch |
| https://github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76 | Patch |
| https://github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff | Mitigation Vendor Advisory |
| https://osv.dev/vulnerability/EEF-CVE-2026-42791 | Third Party Advisory |
| https://www.erlang.org/doc/system/versions.html#order-of-versions | Product |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-42791 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-42791
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-42791 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-42791 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jun. 02, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N Added CPE Configuration OR *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 27.0 up to (excluding) 27.3.4.12 *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 28.0 up to (excluding) 28.5.0.1 *cpe:2.3:a:erlang:erlang/otp:*:*:*:*:*:*:*:* versions from (including) 29.0 up to (excluding) 29.0.1 Added Reference Type EEF: https://cna.erlef.org/cves/CVE-2026-42791.html Types: Third Party Advisory Added Reference Type EEF: https://github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b Types: Patch Added Reference Type EEF: https://github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76 Types: Patch Added Reference Type EEF: https://github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff Types: Mitigation, Vendor Advisory Added Reference Type EEF: https://osv.dev/vulnerability/EEF-CVE-2026-42791 Types: Third Party Advisory Added Reference Type EEF: https://www.erlang.org/doc/system/versions.html#order-of-versions Types: Product -
New CVE Received by 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
May. 27, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 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 Added CWE CWE-295 Added CWE CWE-672 Added Reference https://cna.erlef.org/cves/CVE-2026-42791.html Added Reference https://github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b Added Reference https://github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76 Added Reference https://github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff Added Reference https://osv.dev/vulnerability/EEF-CVE-2026-42791 Added Reference https://www.erlang.org/doc/system/versions.html#order-of-versions