What’s Vulnerable › Vulnerabilities

CVE-2026-93600: rustls webpki Name Constraints URI Validation Bypass

• Severity: low (CVSS 2.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-18 · updated 2026-09-22
• Weakness: CWE-295

Description

rustls-webpki (rustls/webpki) versions 0.101.0 through 0.103.11 and 0.104.0-alpha releases before 0.104.0-alpha.6 ignore X.509 name constraints that apply to URI names, causing such constraints to be accepted rather than enforced. Because name constraints are restrictions on otherwise properly issued certificates, the flaw is only reachable after successful signature verification and requires a misissued certificate to exploit; the library also provides no API for asserting URI names, and URI name constraints are otherwise unimplemented. Versions 0.103.12 and 0.104.0-alpha.6 reject URI name constraints unconditionally.

Affected products

• rustls webpki: from 0.101.0 before 0.103.12; from 0.104.0-alpha.1 before 0.104.0-alpha.6 — fixed in 0.103.12, 0.104.0-alpha.6

How to fix

Upgrade to a fixed version: rustls webpki 0.103.12, 0.104.0-alpha.6. Check the vendor advisory for mitigations.

References

• https://github.com/rustls/webpki/security/advisories/GHSA-965h-392x-2mh5
• https://www.vulncheck.com/advisories/rustls-webpki-name-constraints-uri-validation-bypass

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