Medium severity · published Jun 25, 2026
CVE-2026-6091
Partial-chain verification accepts untrusted intermediate as trust anchor
6.5
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 9% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WO
wolfSSL · wolfSSL
5.7.4 through 5.9.1 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-6091
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-6091
Issue Tracking
https://github.com/wolfSSL/wolfssl/pull/10170
Vendor Advisory
https://www.wolfssl.com/docs/security-vulnerabilities/
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