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webpki: Name constraints were accepted for certificates asserting a wildcard name

Low severity GitHub Reviewed Published Apr 15, 2026 in rustls/webpki • Updated Apr 16, 2026

Package

cargo rustls-webpki (Rust)

Affected versions

>= 0.101.0, < 0.103.12
>= 0.104.0-alpha.1, < 0.104.0-alpha.6

Patched versions

0.103.12
0.104.0-alpha.6

Description

Permitted subtree name constraints for DNS names were accepted for certificates asserting a wildcard name.

This was incorrect because, given a name constraint of accept.example.com, *.example.com could feasibly allow a name of reject.example.com which is outside the constraint.
This is very similar to CVE-2025-61727.

Since name constraints are restrictions on otherwise properly-issued certificates, this bug is reachable only after signature verification and requires misissuance to exploit.

References

@ctz ctz published to rustls/webpki Apr 15, 2026
Published to the GitHub Advisory Database Apr 16, 2026
Reviewed Apr 16, 2026
Last updated Apr 16, 2026

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
High
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N

EPSS score

Weaknesses

Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-xgp8-3hg3-c2mh

Source code

Credits

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