Erlang OTP 27.0-28.4.2: Improper Cert Validation in pubkey_ocsp (OCA Responder Bypass)
CVE-2026-32144 Published on April 7, 2026
OCSP designated-responder authorization bypass via missing signature verification
Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_ocsp module) allows OCSP designated-responder authorization bypass via missing signature verification.
The OCSP response validation in public_key:pkix_ocsp_validate/5 does not verify that a CA-designated responder certificate was cryptographically signed by the issuing CA. Instead, it only checks that the responder certificate's issuer name matches the CA's subject name and that the certificate has the OCSPSigning extended key usage. An attacker who can intercept or control OCSP responses can create a self-signed certificate with a matching issuer name and the OCSPSigning EKU, and use it to forge OCSP responses that mark revoked certificates as valid.
This affects SSL/TLS clients using OCSP stapling, which may accept connections to servers with revoked certificates, potentially transmitting sensitive data to compromised servers. Applications using the public_key:pkix_ocsp_validate/5 API directly are also affected, with impact depending on usage context.
This vulnerability is associated with program files lib/public_key/src/pubkey_ocsp.erl and program routines pubkey_ocsp:is_authorized_responder/3.
This issue affects OTP from OTP 27.0 until OTP 28.4.2 and 27.3.4.10 corresponding to public_key from 1.16 until 1.20.3 and 1.17.1.2, and ssl from 11.2 until 11.5.4 and 11.2.12.7.
Vulnerability Analysis
CVE-2026-32144 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.
Weakness Types
Improper Certificate Validation
The software does not validate, or incorrectly validates, a certificate. When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The software might connect to a malicious host while believing it is a trusted host, or the software might be deceived into accepting spoofed data that appears to originate from a trusted host.
Improper Verification of Cryptographic Signature
The software does not verify, or incorrectly verifies, the cryptographic signature for data.
Products Associated with CVE-2026-32144
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Affected Versions
Erlang OTP:- Version 1.16 and below * is affected.
- Version 11.2 and below * is affected.
- Version 27.0 and below * is affected.
- Version 601a012837ea0a5c8095bf24223132824177124d and below * is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.