CVE-2026-6091 Partial-chain verification accepts untrusted intermediate as trust anchor
Attackers can bypass certificate validation by presenting untrusted intermediate certificates when partial-chain verification is enabled in wolfSSL.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-6091?
CVE-2026-6091 is a medium-severity vulnerability in Wolfssl Wolfssl, published on 25 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Partial-chain certificate verification may accept chains that terminate at a peer-supplied, untrusted intermediate certificate rather than a trusted anchor. An attacker could present a chain that ends at an intermediate they control and have it accepted as valid. This affects the OpenSSL compatibility certificate-path-building path (wolfSSL_X509_verify_cert / X509_STORE, OPENSSL_EXTRA) when the X509_V_FLAG_PARTIAL_CHAIN verify flag is enabled.
Weakness: CWE-295
Which versions are affected by CVE-2026-6091?
It affects 1 product.
Products include Wolfssl Wolfssl.
How do I fix CVE-2026-6091?
Apply the vendor's patch.
Is CVE-2026-6091 being exploited?
There is no known exploitation of CVE-2026-6091 in the wild and no public exploit code.
Other vulnerabilities in Wolfssl Wolfssl
Sources
Also known as DEBIAN-CVE-2026-6091, GHSA-mhq8-94h7-mrgx, JLSEC-2026-742, UBUNTU-CVE-2026-6091.