# CVE-2026-42791: erlang: Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_ocsp module) allows forged OCSP respon...

CVE-2026-42791 is fixed in 37 products on 1 platform, first by SUSE-SU-2026:22082-1, released June 5, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-42791
- Priority: Routine
- CVSS: 3.7 (low)
- EPSS: 0.0032
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 27, 2026

## 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 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | erlang Debian 13.5 (trixie) | 1:27.3.4.1+dfsg-1+deb13u3 | [DEBIAN-CVE-2026-42791](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42791.md) | Jun 24, 2026 |
| Linux | erlang Debian 14 | 1:27.3.4.12+dfsg-1 | [DEBIAN-CVE-2026-42791](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42791.md) | Jun 24, 2026 |
| Linux | erlang Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang opensuse-leap 16.0 | 27.1.3-160000.5.1 | [OPENSUSE-SU-2026:20907-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20907-1.md) | Jun 5, 2026 |
| Linux | erlang sles 16.0 | 27.1.3-160000.5.1 | [SUSE-SU-2026:22082-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-22082-1.md) | Jun 5, 2026 |
| Linux | erlang-asn1 Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-asn1 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-asn1-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-base Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-base 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-base-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-common-test Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-common-test 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-common-test-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-crypto Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-crypto 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-crypto-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-debugger Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-debugger 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-debugger-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-dialyzer Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-dialyzer 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-dialyzer-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-diameter Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-diameter 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-diameter-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-edoc Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-edoc 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-edoc-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-eldap Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-eldap 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-eldap-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-et Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-et 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-et-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-eunit Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-eunit 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-eunit-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-examples Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-examples 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-examples-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-ftp Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-ftp 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-ftp-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-inets Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-inets 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-inets-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-jinterface Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-jinterface 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-jinterface-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-megaco Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-megaco 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-megaco-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-mnesia Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-mnesia 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-mnesia-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-mode Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-mode 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-mode-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-nox Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-nox 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-nox-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-observer Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-observer 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-observer-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-odbc Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-odbc 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-odbc-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-os-mon Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-os-mon 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-os-mon-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-parsetools Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-parsetools 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-parsetools-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-public-key Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-public-key 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-public-key-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-reltool Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-reltool 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-reltool-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-runtime-tools Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-runtime-tools 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-runtime-tools-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-snmp Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-snmp 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-snmp-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-src Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-src 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-src-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-ssh Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-ssh 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-ssh-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-ssl Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-ssl 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-ssl-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-syntax-tools Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-syntax-tools 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-syntax-tools-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-tftp Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-tftp 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-tftp-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-tools Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-tools 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-tools-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-wx Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-wx 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-wx-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-x11 Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-x11 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-x11-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |
| Linux | erlang-xmerl Ubuntu 26.04.1 LTS (resolute) | 1:27.3.4.6+dfsg-1ubuntu0.2 | [erlang-xmerl 1:27.3.4.6+dfsg-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-erlang-xmerl-1-27.3.4.6-dfsg-1ubuntu0.2.md) | Sep 22, 2026 |

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