Executive brief
wolfSSL is a security library used by many applications to provide encrypted communications and verify digital identities. A flaw in how it validates digital certificates allows it to accept signatures that are weaker than they should be. This could allow an attacker to impersonate trusted services or bypass security checks, potentially leading to unauthorized access to sensitive data or systems.
Technical details
A vulnerability exists in wolfSSL's signature verification functions due to missing hash/digest size and OID checks. When verifying ECDSA certificates, the library may accept digests that are smaller than required for the relevant key type or smaller than the standard allows. This issue specifically manifests when EdDSA or ML-DSA is also enabled alongside ECDSA/ECC verification. An attacker could exploit this to weaken the security of certificate-based authentication, provided the public CA key is known. The flaw is categorized as Improper Certificate Validation (CWE-295) and was addressed in version 5.9.1.
Affected products
- wolfSSL Inc. wolfSSL 3.12.0 to 5.9.1 (excluding 5.9.1)
Timeline
- 2026-04-09: advisory: Initial disclosure by wolfSSL Inc.
- 2026-04-16: other: NIST completed initial analysis and assigned CVSS scores.
- 2026-05-23: other: Advisory updated with additional research references.