VU#948176: Multiple TLS Libraries can Bypass Delegation Enforcement

Summary

Overview This note covers thirteen library-specific records (VU#948176.6, .8–.19) of how widely used TLS libraries apply X.509 Name Constraints. The records describe cases where a constrained name may be accepted by one library and rejected by another. Some are fixed, some remain under review, and some were not accepted as security issues. Description Name Constraints are meant to keep a subordinate CA inside an allowed namespace. The records cover several name forms and do not all have the same classification. VU#948176.7 does not exist. DNS case-sensitivity and wildcards. While RFC 5280 requires case-insensitive DNS matching, it does not explicitly define wildcard Subject Alternative Name (SAN) matching, leading to varied implementation behaviors. For instance, GnuTLS was found to perform case-sensitive comparisons on certain names... Related CVEs: CVE-2026-34073, CVE-2026-3547, CVE-2026-3833.

Why it matters

CERT/CC notes often cover coordinated disclosures, multi-vendor exposure, infrastructure risk, or cases where remediation guidance is still developing.

Operator check

Review the CERT/CC Vulnerability Note and compare the affected vendor and product list against your inventory. Apply vendor fixes or compensating controls for Multiple TLS Libraries can Bypass Delegation Enforcement where available.

Sources