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CVE-2026-6091

MEDIUMCVSS 6/10EPSS 0.16%

Last modified

CVE-2026-6091 is a medium-severity vulnerability rated 6/10 on the CVSS scale. 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. EPSS estimates a 0.16% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
6.5/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

CVSS 4.0
6/10

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability
0.16%

5.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
WolfsslWolfssl>= 5.7.4, < 5.9.2

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-6091?
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.
How severe is CVE-2026-6091?
CVE-2026-6091 has a CVSS score of 6/10 (MEDIUM severity). The EPSS model estimates a 0.16% probability of exploitation in the next 30 days.
How do I fix CVE-2026-6091?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-6091?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST