GHSA-394x-vwmw-crm3: Aws lc sys Name Constraints Bypass Vulnerability

HIGH
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CWE-295 CWE-155
Published
Advisory Summary

GHSA-394x-vwmw-crm3 is a HIGH name constraints bypass vulnerability (CWE-295: Improper Certificate Validation) affecting Aws lc sys libraries in the crates.io ecosystem. The issue involves aws-lc x.509 name constraints bypass via wildcard/unicode cn. Remediation is available by upgrading affected packages to version 0.39.0.

GHSA-394x-vwmw-crm3 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-394x-vwmw-crm3
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-295: Improper Certificate Validation
Affected Product Aws lc sys
Package Ecosystem crates.io
Published Date
Last Updated

How to Fix GHSA-394x-vwmw-crm3

To remediate this vulnerability, upgrade all affected Aws lc sys dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

aws-lc-sys fixed: 0.39.0 
Upgrade aws-lc-sys to 0.39.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for aws-lc-sys

How to Check if You Are Affected

To determine whether your application is affected by GHSA-394x-vwmw-crm3, inspect your project dependencies for Aws lc sys:

inspect dependencies for aws-lc-sys

Analyze the terminal output to locate any version of Aws lc sys in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.39.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & RFC 5280 Specification

Under RFC 5280 specifications for X.509 certificates, the Name Constraints extension defines a namespace within which all subsequent subject names in a certification path must be located. Constraints apply to various name forms including directory names, IP addresses, rfc822Name (email addresses), and uniformResourceIdentifier (URI) entries. Specifically, during certificate path validation, affected versions of Aws lc sys failed to properly normalize or enforce boundary checks when domain names contained trailing dot (.) characters. Because domain names with a trailing dot signify fully qualified domain names (FQDNs), this omission allowed non-conforming certificates to be improperly validated as compliant with the defined name constraints.

Source Advisory Statement

### 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](https://aws.amazon.com/security/vulnerability-reporting/) or directly via email to [aws-security@amazon.com](mailto:aws-security@amazon.com). Please do not create a public GitHub issue. ### Credits Oleh Konko from 1seal (https://1seal.org/)

GHSA-394x-vwmw-crm3 Affected Aws lc sys Versions

1 component(s)
Fixed Versions:
0.39.0
Product / Package Ecosystem Affected Versions Fixed Version
aws-lc-sys
 crates.io
≥ 0.32.0
< 0.39.0
0.39.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/aws/aws-lc-rs/security/advisories/GHSA-394x-vwmw-crm3
Aws lc sys Source Repository REPOSITORY
https://github.com/aws/aws-lc-rs
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2026-0044.html

Frequently Asked Questions

What is GHSA-394x-vwmw-crm3?
GHSA-394x-vwmw-crm3 is a security vulnerability in Aws lc sys involving AWS-LC X.509 Name Constraints Bypass via Wildcard/Unicode CN under CWE-295: Improper Certificate Validation.
Which Aws lc sys versions are affected?
Affected versions include releases prior to 0.39.0 across affected packages: aws-lc-sys.
What version fixes GHSA-394x-vwmw-crm3?
Upgrading to 0.39.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is aws-lc-sys affected?
Yes, aws-lc-sys is affected in releases prior to 0.39.0. Upgrade your dependency to 0.39.0 or later.
What CWE is associated with GHSA-394x-vwmw-crm3?
GHSA-394x-vwmw-crm3 is classified under CWE-295: Improper Certificate Validation (The product does not validate, or incorrectly validates, a certificate.).
How can I check crates.io dependencies for GHSA-394x-vwmw-crm3?
Run the dependency tree command: 'inspect dependencies for aws-lc-sys'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-394x-vwmw-crm3",
  "modified" : "2026-03-20T20:34:59Z",
  "published" : "2026-03-20T20:34:59Z",
  "aliases" : [ ],
  "summary" : "AWS-LC X.509 Name Constraints Bypass via Wildcard/Unicode CN",
  "details" : "### Summary\n\nAWS-LC is an open-source, general-purpose cryptographic library.\n\n### Impact\n\nA 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.\n\nCustomers 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.\n\n### Impacted versions:\n\n* aws-lc-sys >= v0.32.0, < v0.39.0\n\n### Patches\n\nThe patch is included in aws-lc-sys v0.39.0.\n\n### Workarounds\n\nApplications 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.\n\nOtherwise, there is no workaround and applications using aws-lc-sys should upgrade to the most recent releases of aws-lc-sys.\n\n### References\n\nIf you have any questions or comments about this advisory, we ask that you contact AWS Security via our [vulnerability reporting page](https://aws.amazon.com/security/vulnerability-reporting/) or directly via email to [aws-security@amazon.com](mailto:aws-security@amazon.com). Please do not create a public GitHub issue.\n\n### Credits\n\nOleh Konko from 1seal (https://1seal.org/)",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "aws-lc-sys"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.32.0"
      }, {
        "fixed" : "0.39.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/aws/aws-lc-rs/security/advisories/GHSA-394x-vwmw-crm3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/aws/aws-lc-rs"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2026-0044.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-155", "CWE-295" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-20T20:34:59Z",
    "nvd_published_at" : null
  }
}