A control character injection vulnerability (CVE-2026-34980, CVSS 7.5 HIGH) in CUPS allows unauthenticated attackers to execute arbitrary code as the `lp` user by sending specially crafted print job requests containing unfiltered control characters in IPP string attributes and PPD keywords. The vulnerability affects CUPS versions up to and including 2.4.16. A patch is available via the Ubuntu security repositories for Ubuntu 16.04 LTS, and the standard system update mechanism should apply the necessary fixes.
Ubuntu Security Notices USN-8578-1 USN-8578-1: CUPS control character injection vulnerability Publication date 21 July 2026 Overview CUPS could be made to run programs as the lp user if it received specially crafted print job requests. Releases 16.04 LTS Open side navigation Close side navigation Packages Details Update instructions References Related notices Packages cups - Common UNIX Printing System(tm) Details It was discovered that CUPS did not properly filter control characters in IPP string attributes and PPD keywords. An unauthenticated attacker could exploit this to execute arbitrary code as the lp user on systems with shared target queues. It was discovered that CUPS did not properly filter control characters in IPP string attributes and PPD keywords. An unauthenticated attacker could exploit this to execute arbitrary code as the lp user on systems with shared target queues. Update instructions In general, a standard system update will make all the necessary changes. Learn more about how to get the fixes. The problem can be corrected by updating your system to the following package versions: Ubuntu Release Package Version 16.04 LTS xenial cups – 2.1.3-4ubuntu0.11+esm13 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. cups-bsd – 2.1.3-4ubuntu0.11+esm13 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. cups-client – 2.1.3-4ubuntu0.11+esm13 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. cups-common – 2.1.3-4ubuntu0.11+esm13 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. cups-core-drivers – 2.1.3-4ubuntu0.11+esm13 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. cups-daemon – 2.1.3-4ubuntu0.11+esm13 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. libcups2 – 2.1.3-4ubuntu0.11+esm13 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. Reduce your security exposure Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines. Get Ubuntu Pro References CVE-2026-34980 CVE-2026-34980 Related notices USN-8405-1 USN-8405-1