# CVE-2026-93600: rustls-webpki X.509 name constraint bypass for URI names

Source: https://junglewise.ai/threats/cve-2026-93600-rustls-webpki-x-509-name-constraint-bypass-for-uri-names  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-18. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-93600 · Severity: low · CVSS 3.1 · Published 2026-09-18

rustls-webpki is a library used by Rust applications to validate X.509 certificates. The library failed to enforce name constraints on URI identifiers in certificates, allowing misissued certificates with URI names to bypass restrictions that should have been applied. Exploitation requires a misissued certificate to reach signature verification, making the practical risk low, though it could allow an attacker with certificate-issuing capability to create certificates that violate organizational policies.

Technologies: [rustls-webpki (crates.io)](https://junglewise.ai/threats/technologies/rustls-webpki), [Rustls Webpki](https://junglewise.ai/threats/technologies/webpki). Vendors: [crates.io](https://junglewise.ai/threats/vendors/crates-io), [Rustls](https://junglewise.ai/threats/vendors/rustls).

## Quick answers

**Is CVE-2026-93600 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-93600 being exploited in the wild.

**How severe is CVE-2026-93600?** Low severity, with a CVSS score of 3.1, published 18 September 2026.

**Which products and versions are affected?** rustls-webpki (crates.io) SEMVER:introduced=0.0.0-0,fixed=0.103.12,introduced=0.104.0-alpha.1,fixed=0.104.0-alpha.6, SEMVER:introduced=0.101.0,fixed=0.103.12; Rustls Webpki 0.101.0 through 0.103.11, 0.104.0-alpha.1 through 0.104.0-alpha.5.

**Is there a fix for CVE-2026-93600?** Yes. rustls-webpki (crates.io): upgrade to 0.103.12, 0.104.0-alpha.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-93600 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-93600?** Check whether you run rustls-webpki (crates.io) or Rustls Webpki at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- rustls-webpki (crates.io): upgrade to 0.103.12, 0.104.0-alpha.6 or later

  ```sh
  cargo update -p rustls-webpki
  ```


## Technical details

The vulnerability is a certificate validation bypass (CWE-295) in name constraint enforcement. rustls-webpki versions 0.101.0–0.103.11 and 0.104.0-alpha through 0.104.0-alpha.5 ignored X.509 name constraints for URI identifiers, accepting certificates that should have been rejected. The flaw exists in the name constraint validation logic and is only reachable after successful certificate signature verification. Exploitation requires a misissued certificate with URI names that violate applied name constraints. The library provides no public API for URI name assertion and URI name constraints are otherwise unimplemented, limiting real-world impact. Versions 0.103.12 and 0.104.0-alpha.6 and later reject URI name constraints unconditionally, fixing the issue.

## Affected products

- Rustls webpki 0.101.0 through 0.103.11, 0.104.0-alpha.1 through 0.104.0-alpha.5

## Identifiers

- CVE-2026-93600
- GHSA-965h-392x-2mh5
- RUSTSEC-2026-0098

## Timeline

- 2026-04-15: disclosed: GitHub Security Advisory (GHSA-965h-392x-2mh5) published
- 2026-04-15: patched: Versions 0.103.12 and 0.104.0-alpha.6 released with fix

## References

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

## Related threats

- [Go crypto/x509 untrusted intermediate certificate validation](https://junglewise.ai/threats/cve-2026-111943-on-most-platforms-go-uses-the-given-system-root-certificates)
- [rustls-webpki CRL distribution point matching bypass](https://junglewise.ai/threats/cve-2026-93602-rustls-webpki-crl-distribution-point-matching-bypass)
- [rustls-webpki name constraint bypass for wildcard certificates](https://junglewise.ai/threats/cve-2026-93601-rustls-webpki-name-constraint-bypass-for-wildcard-certificates)
- [rustls-webpki integer underflow in BIT STRING parsing](https://junglewise.ai/threats/cve-2026-93599-rustls-webpki-integer-underflow-in-bit-string-parsing)
- [rustls-webpki: CPU denial of service in certificate path building](https://junglewise.ai/threats/rustls-webpki-cpu-denial-of-service-in-certificate-path-building-3f07ea21)