RUSTSEC-2026-0044

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`.