CVE-2026-55480
Received Received - Intake

Race Condition in OpenPrinting CUPS Leading to File Overwrite

Publication date: 2026-10-15

Last updated on: 2026-10-15

Assigner: GitHub, Inc.

Description
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.

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Meta Information

Published
2026-10-15
Last Modified
2026-10-15
Generated
2026-10-16
AI Q&A
2026-10-15
EPSS Evaluated
N/A
NVD
CVE-2026-55480
EUVD
EUVD-2026-102205

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
OpenPrinting cups < 2.4.20

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-377 Creating and using insecure temporary files can leave application and system data vulnerable to attack.
CWE-59 The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

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Executive Summary

CVE-2026-55480 is a vulnerability in OpenPrinting CUPS where the copy_model() function in scheduler/ipp.c creates a predictable temporary PPD file path in an lp-group-writable directory. The file is opened as root without O_EXCL or O_NOFOLLOW flags. An attacker with lp-group access can exploit this by creating a symlink at the predictable path, causing the root scheduler to overwrite a root-owned file when opening the PPD file.

Detection Guidance

To detect this vulnerability, check if your CUPS version is below 2.4.20. Run 'cupsd -v' or 'dpkg -l cups' on Debian-based systems to verify the installed version. Inspect the scheduler/ipp.c file for the copy_model() function and check if O_EXCL and O_NOFOLLOW flags are used in open() calls for temporary PPD files.

Impact Analysis

This vulnerability allows an attacker with lp-group membership to overwrite critical root-owned files, potentially leading to file integrity compromise, denial of service, or privilege escalation from lp to root. It requires an existing lp foothold and a privileged printer operation.

Mitigation Strategies

Immediately upgrade CUPS to version 2.4.20 or later. If upgrading is not possible, apply the patches from the GitHub commits referenced in Resources 1 and 2. Restrict lp group membership to trusted users and audit system files for unauthorized modifications.

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