CVE-2023-28321

Name of the Vulnerable Software and Affected Versions curl versions prior to 8.1.0

Description The issue is related to improper certificate validation in the way curl supports matching of wildcard patterns when listed as "Subject Alternative Name" in TLS server certificates. This could lead to incorrect matching of IDN hosts and potentially allow patterns that should mismatch. IDN hostnames are converted to puny code before being used for certificate checks, but the wildcard check in curl could still incorrectly match patterns. This could result in a remote attacker being able to perform a "man-in-the-middle" attack.

Recommendations For versions prior to 8.1.0, update to version 8.1.0 or later to resolve the issue. As a temporary workaround, consider disabling the use of wildcard patterns in TLS server certificates until a patch is available. Restrict access to IDN hostnames to minimize the risk of exploitation. Avoid using the xn-- prefix in wildcard patterns to prevent incorrect matching.