CVE-2026-93601: Cert Validation Flaw (CVSS 2.2)

Description

rustls-webpki (the Rust webpki fork used by rustls) versions >= 0.101.0 and prior to 0.103.12 and 0.104.0-alpha.6 incorrectly accepted permitted-subtree DNS name constraints for certificates asserting a wildcard name. For example, a name constraint of accept.example.com was treated as satisfied by a certificate for *.example.com, which could feasibly assert reject.example.com — a name outside the permitted subtree. Because name constraints are restrictions applied to otherwise properly issued certificates, the issue is only reachable after signature verification succeeds and requires a misissued wildcard certificate to exploit.

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CVSS v3.1 Score

2.2

LOW

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0018

Probability of exploitation

0.07%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-295 CWE-295

References

Other References

https://github.com/rustls/webpki/security/advisories/GHSA-xgp8-3hg3-c2mh https://www.vulncheck.com/advisories/rustls-webpki-0.101.0-before-0.103.12-name-constraint-bypass

Frequently Asked Questions

What is CVE-2026-93601? +

rustls-webpki (the Rust webpki fork used by rustls) versions >= 0.101.0 and prior to 0.103.12 and 0.104.0-alpha.6 incorrectly accepted permitted-subtree DNS name constraints for certificates asserting a wildcard name. For example, a name constraint of accept.example.com was treated as satisfied by a certificate for *.example.com, which could feasibly assert reject.example.com — a name outside the permitted subtree. Because name constraints are restrictions applied to otherwise properly issued certificates, the issue is only reachable after signature verification succeeds and requires a misissued wildcard certificate to exploit. It has a CVSS v3.1 base score of 2.2 (LOW).

How severe is CVE-2026-93601? +

CVE-2026-93601 has a CVSS v3.1 score of 2.2 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0018, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-93601? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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