Microsoft Security Response Center guidance
Vendor revision: Oct 17, 2026Release Notes
Vulnerability intelligence
CVE-2026-55480 and is rated Medium severity with a CVSS score of 5.7. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.
Release Notes
OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. Prior to 2.4.20, copy_model() in scheduler/ipp.c creates a predictable TempDir/<connection-number>.ppd path in an lp-group-writable directory and opens it as root without O_EXCL or O_NOFOLLOW.
Exploitation requires an lp-group process able to write that directory to predict the connection-derived name and plant a symlink before the root open, while a privileged add-printer or modify-printer operation using a model PPD triggers copy_model().
The reporter treats an existing lp foothold and the privileged operation as distinct prerequisites, while the maintainer assesses high privileges because installing the relevant filter or administering the printer requires root or print-administrator access.
If the race succeeds, the root scheduler follows the symlink and truncates or overwrites a root-writable target with generated PPD data, compromising file integrity or availability. This issue is fixed in version 2.4.20.
Source: NVD