RUSTSEC-2026-0099: Name constraints were accepted for certificates asserting a wildcard name

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Details
Package	rustls-webpki
Version	0.103.9
URL	n/a
Patched Versions	>=0.103.12, <0.104.0-alpha.1 OR >=0.104.0-alpha.6
Aliases	GHSA-xgp8-3hg3-c2mh

Permitted subtree name constraints for DNS names were accepted for certificates asserting a wildcard name.

This was incorrect because, given a name constraint of accept.example.com, *.example.com could feasibly allow a name of reject.example.com which is outside the constraint.
This is very similar to CVE-2025-61727.

Since name constraints are restrictions on otherwise properly-issued certificates, this bug is reachable only after signature verification and requires misissuance to exploit.

This vulnerability is identified as GHSA-xgp8-3hg3-c2mh. Thank you to @1seal for the report.