Skip to content
Fencer Vulns
low 3.7

CVE-2026-42791 json

OCSP responder certificate validity period not checked in public_key

published 2026-05-27 5 mo ago modified 2026-10-26 14 d ago also EUVD-2026-32273

cvss
3.7
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

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.

Patch / fix

  • Erlang OTP 1.17.1.3, 1.20.3.1, 1.21.1, 27.3.4.12, 28.5.0.1, 29.0.1
  • erlang Debian 13 1:27.3.4.1+dfsg-1+deb13u3
  • erlang Debian 14 1:27.3.4.12+dfsg-1

debian advisories DEBIAN-CVE-2026-42791

  • erlang Ubuntu 26.04 LTS 1:27.3.4.6+dfsg-1ubuntu0.2

ubuntu advisories UBUNTU-CVE-2026-42791

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • erlang27 hummingbird 1 27.3.4.17-1.hum1
  • erlang27-et hummingbird 1 27.3.4.17-1.hum1
  • erlang27-wx hummingbird 1 27.3.4.17-1.hum1
  • erlang27-ftp hummingbird 1 27.3.4.17-1.hum1
  • erlang27-ssh hummingbird 1 27.3.4.17-1.hum1
  • erlang27-ssl hummingbird 1 27.3.4.17-1.hum1
  • erlang27-asn1 hummingbird 1 27.3.4.17-1.hum1
  • erlang27-edoc hummingbird 1 27.3.4.17-1.hum1

red hat advisories RHSA-2026:63160

  • erlang SLES for SAP applications 16.0, SLES 16.0 27.1.3-160000.5.1

suse advisories SUSE-SU-2026:22082-1

  • erlang openSUSE Tumbleweed 28.5.0.4-1.1
  • erlang openSUSE Leap 16.0 27.1.3-160000.5.1
  • erlang27 openSUSE Tumbleweed 27.1.3-2.1

opensuse advisories openSUSE-SU-2026:11559-1openSUSE-SU-2026:20907-1openSUSE-SU-2026:10947-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-42791 updated cvss 5.9

erlang: Erlang OTP: Authentication bypass due to improper OCSP certificate validation

  • Red Hat Hardened Images erlang27 27.3.4.17-1.hum1, erlang27-et 27.3.4.17-1.hum1, erlang27-wx 27.3.4.17-1.hum1, erlang27-ftp 27.3.4.17-1.hum1, erlang27-ssh 27.3.4.17-1.hum1, erlang27-ssl 27.3.4.17-1.hum1, +33 more
    fixed: vendor fix RHSA-2026:63160
  • Red Hat OpenStack Platform 16.2 erlang, erlang-ssl, erlang-asn1, erlang-erts, erlang-hipe, erlang-sasl, +15 more Red Hat OpenStack Platform 17.1 erlang, erlang-ssl, erlang-asn1, erlang-erts, erlang-sasl, erlang-snmp, +14 more Red Hat OpenStack Platform 18.0 erlang
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
5 mo ago

Exploit prediction

0.32% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 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
CNA 4.0 6.3 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
NVD 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected products

  • Erlang OTP

Classification

Weakness
  • CWE-295 Improper Certificate Validation
  • CWE-672 Operation on a Resource after Expiration or Release

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.