6.3

CVE-2026-42791: erlang erlang\/otp Improper Certificate Validation

CVSS: 6.3v4.0MediumModified
AliasesUBUNTU-CVE-2026-42791DEBIAN-CVE-2026-42791
Published 27-05-2026Last modified 24-07-2026
Open JSON

Vulnerability summary

CVE-2026-42791 is a medium (CVSS 6.3) Improper Certificate Validation vulnerability in erlang erlang\/otp. EPSS estimates a 0.32% chance of exploitation in the next 30 days, higher than 23.5% of scored vulnerabilities.

Overall risk
25/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.3/10
010
Medium · v4.0 (CVE.org)
EPSS score
0.32%
0%100%
Low · +0.01 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 6 · Related 5
OPENSUSE-SU-2026:10947-1OPENSUSE-SU-2026:11559-1OPENSUSE-SU-2026:20907-1RHSA-2026:63160SUSE-SU-2026:22082-1USN-8901-1

Timeline

  1. 27-05-2026
    PublishedVulnerability first disclosed.
  2. 24-07-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

6 scores · 4 sources · 2 versions

EPSS trend

Probability

0.32%

Chance of exploitation in the next 30 days

Percentile

24%

Versus all other CVEs

30-day change

+0.01 pp

From 0.32% on 18-09-2026

18-09-202618-10-2026
EPSS score
0.32%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Erlang2 products
  • erlang\/otp≥ 27.0, < 27.3.4.12 | ≥ 28.0, < 28.5.0.1 | ≥ 29.0, < 29.0.1
  • otp≥ 1.16 (No fix recorded) | ≥ 27.0 (No fix recorded) | ≥ 2b1a742c651b90f8a7a1fb2ddde73f29915ea376 (No fix recorded)
Debian1 product
  • erlang< 1:27.3.4.1+dfsg-1+deb13u3 | < 1:27.3.4.12+dfsg-1
Ubuntu1 product
  • erlangAll versions (No fix recorded) | < 1:27.3.4.6+dfsg-1ubuntu0.2

3 vendors · 4 products

References

10 links