Executive brief
wolfSSL is a security library used to establish encrypted connections for embedded devices and cloud services. A flaw in how it verifies digital certificates could allow an attacker to present a fraudulent certificate that the system incorrectly trusts. This could enable an attacker to impersonate a legitimate service or intercept sensitive data.
Technical details
An improper certificate validation vulnerability exists in wolfSSL's OpenSSL compatibility layer (specifically wolfSSL_X509_verify_cert and X509_STORE). When the X509_V_FLAG_PARTIAL_CHAIN flag is enabled, the certificate-path-building logic may accept a chain that terminates at an untrusted intermediate certificate provided by the peer, rather than a trusted root anchor. An attacker can exploit this by presenting a certificate chain that ends at an intermediate certificate they control. This issue was addressed by ensuring the terminal certificate in a partial chain is a member of the original trust set. The vulnerability affects versions 5.7.4 through 5.9.1 and is fixed in version 5.9.1.
Affected products
- wolfSSL wolfSSL 5.7.4 to 5.9.1
Timeline
- 2026-04-14: patched: Fix merged into master branch via PR 10170
- 2026-06-25: disclosed: CVE published to NVD