rustls webpki Name Constraints URI Validation Bypass (CVE-2026-93600) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-93600

rustls webpki Name Constraints URI Validation Bypass

Answer in brief

CVE-2026-93600 records a Unknown severity vulnerability in rustls webpki Name Constraints URI Validation Bypass. The current sources do not mark it as known exploited. The current feed maps rustls/webpki (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 18, 2026Updated Sep 18, 2026Source checked Sep 18, 2026First seen by HOL Sep 18, 2026Material review Sep 18, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps rustls/webpki (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
rustls/webpkigeneric	>=0.101.0 <0.103.12 \|\| >=0.104.0-alpha.1 <0.104.0-alpha.6	0.103.12, 0.104.0-alpha.6

Recommended response

Check inventory. Check lockfiles and deployed manifests for rustls/webpki.
Review the reported fix. Update rustls/webpki to 0.103.12 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 18, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.