Executive brief
wolfSSL is a security library used to establish encrypted connections for applications and embedded devices. A vulnerability was found where the library fails to properly check certain security restrictions on digital certificates if they do not contain modern 'Subject Alternative Name' fields. This could allow a malicious or compromised certificate authority to issue certificates that bypass intended security boundaries, potentially leading to unauthorized connections being accepted as valid.
Technical details
A vulnerability in wolfSSL's certificate validation logic (CWE-295) allows for a name constraint bypass. When an issuing Certificate Authority (CA) has DNS name constraints defined, wolfSSL only enforces these constraints against the Subject Alternative Name (SAN) extension. If a certificate lacks a SAN extension and instead uses the Subject Common Name (CN) for the DNS identity, the library fails to apply the issuing CA's name constraints to that CN. An attacker with a certificate issued by a constrained CA could use a Subject CN that violates those constraints to impersonate a domain. This issue is fixed in wolfSSL version 5.9.1.
Affected products
- wolfSSL wolfSSL 3.9.10 through 5.9.1
Timeline
- 2026-04-14: other: Fix submitted via GitHub pull request
- 2026-04-19: patched: Fix merged into master branch
- 2026-06-25: disclosed: CVE published to NVD