What’s Vulnerable › Vulnerabilities

CVE-2026-6091: Partial-chain verification accepts untrusted intermediate as trust anchor

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-25 · updated 2026-06-26
• Weakness: CWE-295

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.

Affected products

• wolfSSL: from 5.7.4 before 5.9.2 — fixed in 5.9.2

How to fix

Upgrade to a fixed version: wolfSSL 5.9.2. Check the vendor advisory for mitigations.

References

• https://github.com/wolfSSL/wolfssl/pull/10170
• https://www.wolfssl.com/docs/security-vulnerabilities/

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