CVE-2023-28321: Apple macOS

Medium severity, CVSS 5.9. EPSS: 1.8% chance of exploitation in the next 30 days.

An improper certificate validation vulnerability exists in curl <v8.1.0 in the way it supports matching of wildcard patterns when listed as "Subject Alternative Name" in TLS server certificates. curl can be built to use its own name matching function for TLS rather than one provided by a TLS library. This private wildcard matching function would match IDN (International Domain Name) hosts incorrectly and could as a result accept patterns that otherwise should mismatch. IDN hostnames are converted to puny code before used for certificate checks. Puny coded names always start with `xn--` and should not be allowed to pattern match, but the wildcard check in curl could still check for `x*`, which would match even though the IDN name most likely contained nothing even resembling an `x`.

Affected products

• Apple macOS: from 11.0, before 11.7.9 (fixed in 11.7.9); from 12.0, before 12.6.8 (fixed in 12.6.8); from 13.0, before 13.5 (fixed in 13.5)
• Debian Debian Linux: version 10.0 only
• Fedoraproject Fedora: version 37 only; version 38 only
• Haxx Curl: before 8.1.0 (fixed in 8.1.0)
• Netapp Clustered Data Ontap: affected versions not specified
• Netapp h300s Firmware: affected versions not specified
• Netapp h410s Firmware: affected versions not specified
• Netapp h500s Firmware: affected versions not specified
• Netapp h700s Firmware: affected versions not specified
• Netapp Ontap Antivirus Connector: affected versions not specified

Published 2023-05-26. Last modified 2026-06-17.