CVE-2026-42791: Erlang OTP · Improper Certificate Validation
Affects Erlang OTPSource CVE Database V5
Not known to be exploited · CVSS 6.3 Medium : upgrade to 1.17.1.3 when convenient.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 24% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.17.1.3, 27.3.4.12
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 27 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade OTP and public_key to 1.17.1.3; OTP and erlang/otp to 27.3.4.12.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| ErlangOTP | Affected
| Fixed in
|
| ErlangOTP | Affected
| Fixed in
|
Hexpublic_keypkg:hex/public_keyOther threats | Affected
| Fixed in– |
GitHubpublic_keypkg:github/public_keyOther threats | Affected
| Fixed in
|
GitHuberlang/otppkg:github/erlang/otpOther threats | Affected
| Fixed in
|
CPE configurations (1)
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, users should consider alternative certificate validation methods or additional checks on OCSP responder certificate validity periods outside of Erlang OTP.
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.
References
- github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff (opens in a new tab)
- cna.erlef.org/cves/CVE-2026-42791.html (opens in a new tab)
- osv.dev/vulnerability/EEF-CVE-2026-42791 (opens in a new tab)
- erlang.org/doc/system/versions.html (opens in a new tab)
- github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b (opens in a new tab)
- github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76 (opens in a new tab)