Summary
AWS-LC X.509 Name Constraints Bypass via Wildcard/Unicode CN
AWS-LC is an open-source, general-purpose cryptographic library.
Impacted versions:
- aws-lc-sys >= v0.32.0, < v0.39.0
Workarounds
Applications that set X509_CHECK_FLAG_NEVER_CHECK_SUBJECT to disable CN fallback are not affected. Applications that only encounter certificates with dNSName SANs (standard for public WebPKI) are also not affected.
Otherwise, there is no workaround and applications using aws-lc-sys should upgrade to the most recent releases of aws-lc-sys.
References
If you have any questions or comments about this advisory, we ask that you contact AWS Security via our vulnerability reporting page or directly via email to [email protected]. Please do not create a public GitHub issue.
Credits
Oleh Konko from 1seal (https://1seal.org/)
Impact
A logic error in CN (Common Name) validation allows certificates with wildcard or raw UTF-8 Unicode CN values to bypass name constraints enforcement. The cn2dnsid function does not recognize these CN patterns as valid DNS identifiers, causing NAME_CONSTRAINTS_check_CN to skip validation. However, X509_check_host accepts these CN values when no dNSName SAN is present, allowing certificates to bypass name constraints while still being used for hostname verification.
Customers of AWS services do not need to take action. Applications using aws-lc-sys should upgrade to the most recent release of aws-lc-sys.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The patch is included in aws-lc-sys v0.39.0.
Frequently Asked Questions
- What is GHSA-394X-VWMW-CRM3? GHSA-394X-VWMW-CRM3 is a high-severity security vulnerability in aws-lc-sys (rust), affecting versions >= 0.32.0, < 0.39.0. It is fixed in 0.39.0.
- Which versions of aws-lc-sys are affected by GHSA-394X-VWMW-CRM3? aws-lc-sys (rust) versions >= 0.32.0, < 0.39.0 is affected.
- Is there a fix for GHSA-394X-VWMW-CRM3? Yes. GHSA-394X-VWMW-CRM3 is fixed in 0.39.0. Upgrade to this version or later.
- Is GHSA-394X-VWMW-CRM3 exploitable, and should I be worried? Whether GHSA-394X-VWMW-CRM3 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-394X-VWMW-CRM3 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-394X-VWMW-CRM3? Upgrade
aws-lc-systo 0.39.0 or later.