CVE-2026-103602: Cert Validation Flaw

Description

Improper certificate validation in PkixNameConstraintValidator in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who controls, or can obtain certificates from, a name-constrained intermediate CA to have certificates accepted during PKIX certification path validation for email addresses, DNS names or URI hosts that lie within excluded subtrees applying to that CA, via an rfc822Name, dNSName or uniformResourceIdentifier name whose host ends with a dot, because names and constraints were compared without first removing the RFC 1034 root-label trailing dot, so a fully qualified host name did not match an excluded subtree for the same host written without the dot.

Is your site exposed to CVE-2026-103602?

Run a free security scan — no signup, results in seconds.

EPSS — Exploit Prediction

0.0024

Probability of exploitation

0.14%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-295 CWE-295

References

Other References

https://github.com/bcgit/bc-csharp/commit/75c3c576602886180ed92a63c89419e3bd63b392 https://github.com/bcgit/bc-csharp/commit/be276e057775a6a674a62e9d9a2583b229978f73 https://github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09 https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103602

Frequently Asked Questions

What is CVE-2026-103602? +

Improper certificate validation in PkixNameConstraintValidator in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who controls, or can obtain certificates from, a name-constrained intermediate CA to have certificates accepted during PKIX certification path validation for email addresses, DNS names or URI hosts that lie within excluded subtrees applying to that CA, via an rfc822Name, dNSName or uniformResourceIdentifier name whose host ends with a dot, because names and constraints were compared without first removing the RFC 1034 root-label trailing dot, so a fully qualified host name did not match an excluded subtree for the same host written without the dot.

How do I check if I'm vulnerable to CVE-2026-103602? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-44700

Elixir WebRTC is an Elixir implementation of the W3C WebRTC API. Prior to 0.15.1 and 0.16.1, missing DTLS peer certificate …

CVE-2025-9291

A certification validation weakness exists in communication between affected Omada devices and cloud controllers. Certificate identity verification does not adequately …

CVE-2026-0277

An improper certificate validation vulnerability in the Prisma® Access Agent for iOS enables an attacker to perform a man-in-the-middle (MitM) …

CVE-2025-3463

"This issue is limited to motherboards and does not affect laptops, desktop computers, or other endpoints." An insufficient validation vulnerability …

CVE-2025-5279

When the Amazon Redshift Python Connector is configured with the BrowserAzureOAuth2CredentialsProvider plugin, the driver skips the SSL certificate validation step …

CVE-2025-34066

An improper certificate validation vulnerability exists in AVTECH IP cameras, DVRs, and NVRs due to the use of wget with …

CVE-2026-103602