GHSA-394x-vwmw-crm3 RUSTSEC-2026-0044
AWS-LC X.509 Name Constraints Bypass via Wildcard/Unicode CN
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/)
Affected versions
crates.io
| Package | Vulnerable | Fixed in |
|---|---|---|
| aws-lc-sys | >= 0.32.0, < 0.39.0 |
0.39.0 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
aws-lc-sys crates.io → 0.39.0
- cargo
cargo update -p aws-lc-sys --precise 0.39.0
Severity breakdown
CVSS 4.0 0.0
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
- Attack vector
- Network
- Attack complexity
- High
- Attack requirements
- Present
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- High
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
Weakness
CWE-155: Improper Neutralization of Wildcards or Matching Symbols
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as wildcards or matching symbols when they are sent to a downstream component.
How to prevent it
- Developers should anticipate that wildcard or matching elements will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Implementation: While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (CWE-88).
- Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
CWE-295: Improper Certificate Validation
The product does not validate, or incorrectly validates, a certificate.
How to prevent it
- Architecture and Design, Implementation: Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
- Implementation: If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
References
Packages
Other links
Timeline
- Published
- Last updated by the source
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-9f94-5g5w-gf6r CRL Distribution Point Scope Check Logic Error in AWS-LC | Critical | Also affects aws-lc-sys |
| GHSA-vw5v-4f2q-w9xf AWS-LC has PKCS7_verify Certificate Chain Validation Bypass | High | Also affects aws-lc-sys |
| GHSA-hfpc-8r3f-gw53 AWS-LC has PKCS7_verify Signature Validation Bypass | High | Also affects aws-lc-sys |
| GHSA-65p9-r9h6-22vj AWS-LC has Timing Side-Channel in AES-CCM Tag Verification | Medium | Also affects aws-lc-sys |
| GHSA-wpmr-8h3q-fwj7 Open WebUI: Sign-in as another user via wildcard characters in the OAuth subject claim on SQLite | High | Same weakness, CWE-155 |
| GHSA-78fx-h6xr-vch4 Laravel has a File Validation Bypass | Critical | Same weakness, CWE-155 |
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