CVE-2026-42791Network attack vector

Revoked-certificate acceptance via expired responder certificate

Published May 27, 2026 · Updated May 27, 2026

OCSP validation in Erlang/OTP 27 before 27.3.4.12, 28 before 28.5.0.1, and 29 before 29.0.1 accepts forged responses from attackers. pubkey_ocsp:verify_response/5 reaches is_authorized_responder/3 without checking the responder certificate's notBefore or notAfter fields. Exploitation requires an expired CA-designated responder private key and a controlled server or man-in-the-middle position, causing a revoked peer certificate to be trusted.

CVSS severity6.3
Medium
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

OCSP validation in Erlang/OTP 27 before 27.3.4.12, 28 before 28.5.0.1, and 29 before 29.0.1 accepts forged responses from attackers. pubkey_ocsp:verify_response/5 reaches is_authorized_responder/3 without checking the responder certificate's notBefore or notAfter fields. Exploitation requires an expired CA-designated responder private key and a controlled server or man-in-the-middle position, causing a revoked peer certificate to be trusted.

The record

CVE
CVE-2026-42791
Published
May 27, 2026
Updated
May 27, 2026
Vendor
Erlang
Product
Erlang/OTP
Classifications
CWE-672, CWE-295, CAPEC-475, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 27, 2026CVE publishedPublication date reported by the CVE source.
  2. May 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.16 <* changes=[{"at":"1.17.1.3","status":"unaffected"},{"at":"1.20.3.1","status":"unaffected"},{"at":"1.21.1","status":"unaffected"}]
  2. Affected versionversion=27.0 <* changes=[{"at":"27.3.4.12","status":"unaffected"},{"at":"28.5.0.1","status":"unaffected"},{"at":"29.0.1","status":"unaffected"}]
  3. Affected versionversion=2b1a742c651b90f8a7a1fb2ddde73f29915ea376 <* changes=[{"at":"7995f1fdaee3da569bb810358ce0f546471d169b","status":"unaffected"},{"at":"b3870e02405c709a872b01ba6086065620cdfe76","status":"unaffected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Erlang · Erlang/OTPversion=1.16 <* changes=[{"at":"1.17.1.3","status":"unaffected"},{"at":"1.20.3.1","status":"unaffected"},{"at":"1.21.1","status":"unaffected"}]; version=27.0 <* changes=[{"at":"27.3.4.12","status":"unaffected"},{"at":"28.5.0.1","status":"unaffected"},{"at":"29.0.1","status":"unaffected"}]; version=2b1a742c651b90f8a7a1fb2ddde73f29915ea376 <* changes=[{"at":"7995f1fdaee3da569bb810358ce0f546471d169b","status":"unaffected"},{"at":"b3870e02405c709a872b01ba6086065620cdfe76","status":"unaffected"}]

Published CVSS scores

6.3Erlang Ecosystem FoundationCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N
3.7NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-672Operation on a Resource after Expiration or Release
CWE-295Improper Certificate Validation
CAPEC-475Signature Spoofing by Improper Validation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo