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A critical flaw in Bouncy Castle Java certificate validation, tracked as CVE-2026-8763, allows attackers to bypass Name Constraints checks by appending a trailing dot to rfc822Name and URI values in certificates. The bug affects Bouncy Castle for Java before 1.85, BC-LTS before 2.73.12, and Bouncy Castle FIPS (BC-FJA) before 1.0.2.7, 2.0.2, and 2.1.3, and carries a CVSS 4.0 score of 9.3. The weakness is classified as CWE-295: Improper Certificate Validation and is considered remotely exploitable without privileges or user interaction.
Project maintainers said the issue stems from inconsistent handling of trailing dots in PKIXNameConstraintValidator: dNSName values were normalized for comparison, but rfc822Name and URI values were not, enabling excluded subtree checks to be evaded. An attacker controlling a name-constrained intermediate CA could issue certificates for email addresses or URI hosts that policy should have blocked. The vulnerable path is reachable through the Java 8+ PKIX certificate validation flow, and fixes were released in the patched versions above, including commit 2c28b253a446.
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The bc-java project published a wiki advisory describing how trailing dots in rfc822Name and URI comparisons could bypass excluded subtree checks during certificate path validation. The advisory documented affected versions, exploitation conditions, and the fixing commit.
CVE-2026-8763 was published as a critical Bouncy Castle Java vulnerability involving improper certificate validation and a Name Constraints bypass. The issue affects BC before 1.85, BC-LTS before 2.73.12, and BC-FJA before 1.0.2.7, 2.0.2, and 2.1.3.
Bouncy Castle fixed a certificate path validation flaw in PKIXNameConstraintValidator that allowed Name Constraints bypass via trailing dots in rfc822Name and URI values. The fix was released in BC 1.85, BC-LTS 2.73.12, and BC-FJA 1.0.2.7, 2.0.2, and 2.1.3, with the change introduced in commit 2c28b253a446.
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CERT/CC disclosed **CVE-2026-9648** in the Haskell library `crypton-x509-validation`, warning that affected TLS clients may accept certificates that violate X.509 `NameConstraints`. The flaw stems from the library not enforcing the RFC 5280 safeguard, which can let an attacker who has compromised a name-constrained subordinate CA create certificates for domains outside the CA’s authorized scope and use them in malicious TLS interception. The vulnerability carries a **CVSS 9.1** rating and can expose organizations to credential theft, secret theft, and disclosure of sensitive financial data, particularly in delegated PKI environments such as banks, insurers, and large enterprises. **All prior versions are affected**, and the issue has been fixed in `crypton-x509-validation` **1.9.1**; maintainers and CERT/CC urged Haskell teams to upgrade immediately.
Jun 29, 2026
An **Important** vulnerability tracked as `CVE-2026-33810` affects Go's `crypto/x509` package and can allow a certificate validation bypass during trusted certificate chain verification. The flaw stems from excluded DNS constraints not being correctly applied to wildcard DNS Subject Alternative Names when the SAN's case differs from the constraint, creating a path for a malicious certificate to be accepted when it should be rejected. Red Hat assigned the issue a **CVSS v3 score of 8.8** and warned that affected products could accept malicious certificates from otherwise trusted chains, weakening the certificate trust model. Red Hat said multiple affected products and components have been fixed through security errata, while the CVE record formally tracks the issue as `CVE-2026-33810`.
Aug 20, 2026
Go disclosed **CVE-2026-33810**, a certificate validation flaw in `crypto/x509` in Go 1.26 that can cause excluded DNS name constraints to be enforced incorrectly for wildcard Subject Alternative Names. The bug appears when a wildcard SAN such as `*.example.com` is evaluated against an excluded constraint written with different letter casing, such as `EXAMPLE.COM`, allowing the wildcard domain to bypass the exclusion during certificate chain verification. The issue affects otherwise trusted certificate chains anchored in `VerifyOptions.Roots` or the system certificate pool, narrowing exposure to chains that already terminate at a trusted root CA. Go tracked the bug as issue **#78332**, credited the report to Riyas from Saintgits College of Engineering, k1rnt, and @1seal, and later published a fix on the `release-branch.go1.26`; downstream vendors including SUSE also opened advisories for the vulnerability.
Jun 29, 2026