CVE-2026-93601 — rustls webpki 0.101.0 before 0.103.12 Name Constraint Bypass

Affected: rustls webpki

rustls-webpki (the Rust webpki fork used by rustls) versions >= 0.101.0 and prior to 0.103.12 and 0.104.0-alpha.6 incorrectly accepted permitted-subtree DNS name constraints for certificates asserting a wildcard name. For example, a name constraint of accept.example.com was treated as satisfied by a certificate for *.example.com, which could feasibly assert reject.example.com — a name outside the permitted subtree. Because name constraints are restrictions applied to otherwise properly issued certificates, the issue is only reachable after signature verification succeeds and requires a misissued wildcard certificate to exploit.

GHSA-xgp8-3hg3-c2mh — webpki: Name constraints were accepted for certificates asserting a wildcard name

Affected: crates.io: rustls-webpki

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](https://go.dev/issue/76442).

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

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CVE-2026-93601 — rustls webpki 0.101.0 before 0.103.12 Name Constraint Bypass

GHSA-xgp8-3hg3-c2mh — webpki: Name constraints were accepted for certificates asserting a wildcard name