CVE-2026-55964 Details
Description
Chain intermediate CA:TRUE without keyCertSign accepted as a signing CA. Intermediate CA certificates are required to have the keyCertSign key usage when a Key Usage extension is present, but chain-supplied temporary CAs (WOLFSSL_TEMP_CA) added while building a certificate path were previously exempted from this check, so an intermediate asserting CA:TRUE but lacking keyCertSign was accepted as a signing CA. The check now applies to chain-supplied temporary CAs as well; only operator-loaded root certificates (WOLFSSL_USER_CA) and self-signed roots remain exempt. Per RFC 5280 an absent Key Usage extension implies all usages, so the requirement is enforced only when the extension is actually present (extKeyUsageSet). Affects the OpenSSL-compatibility certificate-path-building path (X509_verify_cert / X509_STORE, OPENSSL_EXTRA/OPENSSL_ALL), where untrusted chain intermediates are added as temporary CAs; native (non-OpenSSL-compat) certificate verification does not create temporary CAs and is unaffected. Within those builds, the check applies unless ALLOW_INVALID_CERTSIGN is defined.
A vulnerability exists in wolfSSL's certificate path validation process, specifically in the OpenSSL compatibility layer. Intermediate CA certificates are required to have the keyCertSign usage when the Key Usage extension is present. However, temporary CAs added from the chain during certificate path building were previously exempt from this requirement. This allowed an intermediate CA to be accepted as a signing authority even without the keyCertSign usage, creating a potential for misuse. The vulnerability has been addressed by applying the key usage check to all chain-supplied temporary CAs, except for operator-loaded root certificates and self-signed roots. The issue is relevant to wolfSSL versions through 5.8.4, when the OpenSSL compatibility layer is active, and ALLOW_INVALID_CERTSIGN is not defined.
Users are advised to update to wolfSSL version 5.9.1 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 26, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/wolfSSL/wolfssl/pull/10702 | [email protected] | Issue TrackingPatch |
| https://www.wolfssl.com/docs/security-vulnerabilities/ | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-295 | Improper Certificate Validation | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| wolfssl wolfssl | >= 5.7.4, < 5.9.2 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 26, 2026 | Initial Analysis | [email protected] |
| Jun 26, 2026 | CVE Modified | CISA-ADP |
| Jun 25, 2026 | New CVE Received | [email protected] |