CVE-2026-55964
Chain intermediate CA:TRUE without keyCertSign accepted as a signing CA (temporary CA exemption)
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.
INFO
Published Date :
June 25, 2026, 7:30 p.m.
Last Modified :
June 25, 2026, 7:30 p.m.
Remotely Exploit :
Yes !
Source :
wolfSSL
Affected Products
The following products are affected by CVE-2026-55964
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | MEDIUM | 50d2cd11-d01a-48ed-9441-5bfce9d63b27 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update WOLFSSL library to the latest version.
- Ensure intermediate CA certificates have keyCertSign usage.
- Avoid using temporary CAs unless necessary.
- Define ALLOW_INVALID_CERTSIGN if needed.
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CVE-2026-55964 vulnerability anywhere in the article.