CVE-2026-32144
Published: 07 April 2026
Summary
CVE-2026-32144 is a high-severity Improper Certificate Validation (CWE-295) vulnerability in Erlang Erlang\/Otp. Its CVSS base score is 7.6 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Adversary-in-the-Middle (T1557); ranked at the 12.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SC-17 (Public Key Infrastructure Certificates) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-32144 is an Improper Certificate Validation vulnerability in the Erlang/OTP public_key module's pubkey_ocsp component, specifically affecting the public_key:pkix_ocsp_validate/5 function and the pubkey_ocsp:is_authorized_responder/3 routine in lib/public_key/src/pubkey_ocsp.erl. The flaw enables an OCSP designated-responder authorization bypass because the validation does not cryptographically verify that the responder certificate is signed by the issuing CA; it only checks for a matching issuer name and the presence of the OCSPSigning extended key usage. This impacts Erlang/OTP (OTP) versions from 27.0 up to but excluding 28.4.2 and 27.3.4.10, corresponding to public_key versions 1.16 to 1.20.3 and 1.17.1.2, and ssl versions 11.2 to 11.5.4 and 11.2.12.7.
A network-based attacker (AV:N) with no privileges (PR:N) can exploit this via interception or control of OCSP responses, forging them by creating a self-signed certificate with a matching issuer name and OCSPSigning EKU to mark revoked certificates as valid. Exploitation requires high complexity (AC:H) but has no user interaction (UI:N), with a CVSS v3.1 base score of 7.4 (C:H/I:H/A:N/S:U). SSL/TLS clients using OCSP stapling may accept connections to servers with revoked certificates, enabling transmission of sensitive data to compromised servers. Applications directly invoking public_key:pkix_ocsp_validate/5 face similar risks depending on their OCSP usage context.
Advisories and patches, detailed in the Erlang CNA report, GitHub security advisory GHSA-gxrm-pf64-99xm, and OSV entry, recommend upgrading to fixed OTP releases such as 28.4.2 or 27.3.4.10 (with corresponding public_key 1.20.3/1.17.1.2 and ssl 11.5.4/11.2.12.7). Relevant patches are available in GitHub commits 49033a6d93a5be0ee0dce04e1fb8b4ae7de1e0c0 and ac7ff528be857c5d35eb29c7f24106e3a16d4891.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-19604
Vulnerability details
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.…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability enables forged OCSP responses (via responder cert bypass) that succeed only when an adversary intercepts or controls OCSP traffic, directly facilitating Adversary-in-the-Middle attacks against TLS clients.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mitigates the CVE by requiring timely patching of the vulnerable Erlang/OTP public_key and ssl modules to versions that properly verify OCSP responder certificate signatures.
Requires management of PKI certificates including validation of OCSP responder certificates via cryptographic signature checks by the issuing CA, preventing authorization bypass.
Ensures receipt, dissemination, and implementation of vendor security advisories like GHSA-gxrm-pf64-99xm for this OCSP validation flaw, enabling prompt remediation.