GHSA-394x-vwmw-crm3 — aws-lc-sys
GHSA-394x-vwmw-crm3 is a security vulnerability in aws-lc-sys. A fix is available for aws-lc-sys — see the affected versions and patch details below.
AWS-LC X.509 Name Constraints Bypass via Wildcard/Unicode CN
Real-World Exposure
aws-lc-sysReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Summary
AWS-LC is an open-source, general-purpose cryptographic library.
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.
Impacted versions:
- aws-lc-sys >= v0.32.0, < v0.39.0
Patches
The patch is included in aws-lc-sys 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/)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | aws-lc-sys | ≥ 0.32.0&&< 0.39.0 | 0.39.0cargo update -p aws-lc-sys --precise 0.39.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aws-lc-sys, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update aws-lc-sys to 0.39.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-394x-vwmw-crm3 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-394x-vwmw-crm3 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-394x-vwmw-crm3. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-394x-vwmw-crm3 in your dependencies?
O3 Security finds GHSA-394x-vwmw-crm3 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.