Bug 2538296 (CVE-2026-93600)

Summary: CVE-2026-93600 rustls-webpki: rustls-webpki: URI Name Constraint Bypass via X.509 Certificate Misissue
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in rustls-webpki where the library incorrectly ignores X.509 name constraints that apply to Uniform Resource Identifier (URI) names. This issue causes these constraints to be accepted rather than properly enforced. Exploitation requires a misissued certificate and successful signature verification, potentially allowing a bypass of intended certificate restrictions.
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Bug Depends On: 2548156, 2548157, 2548159, 2548165, 2548166, 2548167, 2548168, 2548169, 2548170, 2548173, 2548175, 2548158, 2548160, 2548162, 2548164, 2548171, 2548172, 2548174, 2548176, 2548182, 2548183    
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Description OSIDB Bzimport 2026-09-22 17:39:10 UTC 
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.