CVE-2026-93601: Rustls Webpki

Low severity, CVSS 2.2. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Rustls Webpki: from 0.101.0, before 0.103.12 (fixed in 0.103.12); from 0.104.0-alpha.1, before 0.104.0-alpha.6 (fixed in 0.104.0-alpha.6)

Published 2026-09-18. Last modified 2026-09-22.