CVE-2026-93600: Improper Certificate Validation in rustls webpki
CVE-2026-93600 is a low-severity vulnerability in rustls-webpki affecting versions 0.101.0 through 0.103.11 and 0.104.0-alpha releases before 0.104.0-alpha.6. The flaw causes the library to ignore X.509 name constraints that apply to URI names, accepting them rather than enforcing restrictions. This issue requires a misissued certificate and successful signature verification to be exploitable. Later versions 0.103.12 and 0.104.0-alpha.6 address the issue by rejecting URI name constraints unconditionally.
AI Analysis
Technical Summary
The rustls-webpki library versions 0.101.0 through 0.103.11 and 0.104.0-alpha releases prior to 0.104.0-alpha.6 improperly validate X.509 name constraints related to URI names. Instead of enforcing these constraints, the library accepts them, which could allow a misissued certificate to bypass intended restrictions. This vulnerability is only reachable after successful signature verification and requires a misissued certificate to exploit. The library lacks an API for asserting URI names, and URI name constraints are otherwise unimplemented. Versions 0.103.12 and 0.104.0-alpha.6 fix this by rejecting URI name constraints unconditionally.
Potential Impact
The vulnerability allows acceptance of URI name constraints that should be restricted, potentially enabling misuse of misissued certificates after signature verification. However, exploitation requires a misissued certificate and conditions that limit the practical impact. The CVSS 4.0 base score is 2.1, indicating low severity.
Mitigation Recommendations
Upgrade rustls-webpki to version 0.103.12 or later, or to 0.104.0-alpha.6 or later, where URI name constraints are rejected unconditionally. No other mitigation is indicated.
CVE-2026-93600: Improper Certificate Validation in rustls webpki
Description
CVE-2026-93600 is a low-severity vulnerability in rustls-webpki affecting versions 0.101.0 through 0.103.11 and 0.104.0-alpha releases before 0.104.0-alpha.6. The flaw causes the library to ignore X.509 name constraints that apply to URI names, accepting them rather than enforcing restrictions. This issue requires a misissued certificate and successful signature verification to be exploitable. Later versions 0.103.12 and 0.104.0-alpha.6 address the issue by rejecting URI name constraints unconditionally.
CVSS v4.0
Score 2.1low
Affected software
rustls
webpki
pkg:cargo/rustls/webpkiRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The rustls-webpki library versions 0.101.0 through 0.103.11 and 0.104.0-alpha releases prior to 0.104.0-alpha.6 improperly validate X.509 name constraints related to URI names. Instead of enforcing these constraints, the library accepts them, which could allow a misissued certificate to bypass intended restrictions. This vulnerability is only reachable after successful signature verification and requires a misissued certificate to exploit. The library lacks an API for asserting URI names, and URI name constraints are otherwise unimplemented. Versions 0.103.12 and 0.104.0-alpha.6 fix this by rejecting URI name constraints unconditionally.
Potential Impact
The vulnerability allows acceptance of URI name constraints that should be restricted, potentially enabling misuse of misissued certificates after signature verification. However, exploitation requires a misissued certificate and conditions that limit the practical impact. The CVSS 4.0 base score is 2.1, indicating low severity.
Mitigation Recommendations
Upgrade rustls-webpki to version 0.103.12 or later, or to 0.104.0-alpha.6 or later, where URI name constraints are rejected unconditionally. No other mitigation is indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-09-18T11:00:32.756Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6aad3d5d55bf5e2cf5100793
Added to database: 09/18/2026, 13:32:13 UTC
Last enriched: 09/18/2026, 13:47:35 UTC
Last updated: 09/18/2026, 18:58:41 UTC
Views: 8
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