GHSA-394x-vwmw-crm3
AWS-LC X.509 Name Constraints Bypass via Wildcard/Unicode CN
GHSA-394x-vwmw-crm3 is a high vulnerability (CVSS 8.2) in aws-lc-sys, published March 19, 2026. No source lists public exploit code. Fixed in aws-lc-sys 0.39.0.
- Severity
- 8.2 HighCVSS 4.0, GitHub Advisories
- Exploit chance
- UnscoredNo EPSS score yet
- Exploitation
- None knownNot on CISA’s or ENISA’s lists
- Fixed in
0.39.0aws-lc-sys
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 aws-security@amazon.com. Please do not create a public GitHub issue.
Credits
Oleh Konko from 1seal (https://1seal.org/)
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Affected packages
| Package | Affected | Fixed |
|---|---|---|
aws-lc-syscrates.io | 0.32.0 up to 0.39.0 | 0.39.0 |
What each source reports
GitHub Advisories Score used
AWS-LC X.509 Name Constraints Bypass via Wildcard/Unicode CN
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 aws-security@amazon.com. Please do not create a public GitHub issue.
Credits
Oleh Konko from 1seal (https://1seal.org/)
- Record
GHSA-394x-vwmw-crm3- CVSS 4.0
- 8.2 High
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 - Weakness
- CWE-155, CWE-295
- Updated
- 2026-11-02
OSV
AWS-LC X.509 Name Constraints Bypass via Wildcard/Unicode CN
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 aws-security@amazon.com. Please do not create a public GitHub issue.
Credits
Oleh Konko from 1seal (https://1seal.org/)
- Record
GHSA-394x-vwmw-crm3- CVSS 4.0
- 8.2 High
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 - Weakness
- CWE-155, CWE-295
- Updated
- 2026-11-02
OSVRUSTSEC-2026-0044No score
AWS-LC X.509 Name Constraints Bypass via Wildcard/Unicode CN
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.
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.
- Record
RUSTSEC-2026-0044- Updated
- 2026-11-09
History
| Recorded | Changed | Sources |
|---|---|---|
| facts, references | OSV | |
| first indexed | GitHub Advisories, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.