Is CVE-2026-6731 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-6731 being exploited in the wild.

How severe is CVE-2026-6731?

Informational severity, with a CVSS score of 6, published 25 June 2026.

Is there a fix for CVE-2026-6731?

A patch was published on 2026-04-19: Fix merged into master branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-6731 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-6731?

Check whether you run Wolfssl at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-6731: wolfSSL X.509 name constraint bypass in Subject Common Name

CVE-2026-6731 · Severity: info · CVSS 6 · Published 2026-06-25

wolfSSL is a security library used to establish encrypted connections for applications and embedded devices. A vulnerability was found where the library fails to properly check certain security restrictions on digital certificates if they do not contain modern 'Subject Alternative Name' fields. This could allow a malicious or compromised certificate authority to issue certificates that bypass intended security boundaries, potentially leading to unauthorized connections being accepted as valid.

Technologies: Wolfssl. Vendors: Wolfssl.

Quick answers

Is CVE-2026-6731 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-6731 being exploited in the wild.
How severe is CVE-2026-6731?: Informational severity, with a CVSS score of 6, published 25 June 2026.
Which products and versions are affected?: Wolfssl 3.9.10 through 5.9.1.
Is there a fix for CVE-2026-6731?: A patch was published on 2026-04-19: Fix merged into master branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-6731 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-6731?: Check whether you run Wolfssl at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A vulnerability in wolfSSL's certificate validation logic (CWE-295) allows for a name constraint bypass. When an issuing Certificate Authority (CA) has DNS name constraints defined, wolfSSL only enforces these constraints against the Subject Alternative Name (SAN) extension. If a certificate lacks a SAN extension and instead uses the Subject Common Name (CN) for the DNS identity, the library fails to apply the issuing CA's name constraints to that CN. An attacker with a certificate issued by a constrained CA could use a Subject CN that violates those constraints to impersonate a domain. This issue is fixed in wolfSSL version 5.9.1.

Affected products

wolfSSL wolfSSL 3.9.10 through 5.9.1

Timeline

2026-04-14: other: Fix submitted via GitHub pull request
2026-04-19: patched: Fix merged into master branch
2026-06-25: disclosed: CVE published to NVD

References

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