A public proof-of-concept (PoC) has been released for CVE-2026-39875, an macOS vulnerability in the Common UNIX Printing System (CUPS) that enables an unprivileged local user to perform arbitrary file writes with root privileges. The PoC, published by security researcher Dallas Dubs, showcases how two logic flaws in the privileged cupsd printing daemon can be chained. Although the public code demonstrates a root-level arbitrary file write rather than an interactive root shell, such capability could realistically lead to local privilege escalation based on targeted files and system configurations.
An attacker with access to a standard local account could exploit this condition by modifying configuration files, scheduled task definitions, or application support files in insecure locations.
The practical impact will vary based on SIP restrictions, file permissions, endpoint security controls, and the availability of a suitable target for turning the write into persistent root-level code execution. Organizations should prioritize deploying these updates, especially on shared Mac systems, developer endpoints, and devices where users can execute untrusted local software. Security teams should also watch for unusual local printer registrations, unexpected changes to printer device URIs, and suspicious print jobs targeting file-based destinations.
The PoC release increases the likelihood of active testing and attempted exploitation, making prompt patching crucial.
