CVE-2026-34978: OpenPrinting CUPS: Path traversal in RSS notify-recipient-uri enables file write outside CacheDir/rss (and clobbering of job.cache)
OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.16 and prior, the RSS notifier allows .. path traversal in notify-recipient-uri (e.g., rss:///../job.cache), letting a remote IPP client write RSS XML bytes outside CacheDir/rss (anywhere that is lp-writable). In particular, because CacheDir is group-writable by default (typically root:lp and mode 0770), the notifier (running as lp) can replace root-managed state files via temp-file + rename(). This PoC clobbers CacheDir/job.cache with RSS XML, and after restarting cupsd the scheduler fails to parse the job cache and previously queued jobs disappear. At time of publication, there are no publicly available patches.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-34978?
CVE-2026-34978 has been classified as a high severity vulnerability due to its potential for unauthorized file writes.
How do I fix CVE-2026-34978?
To fix CVE-2026-34978, it is recommended to upgrade OpenPrinting CUPS to version 2.4.17 or later.
What systems are affected by CVE-2026-34978?
CVE-2026-34978 affects OpenPrinting CUPS versions 2.4.16 and earlier.
What is the main impact of CVE-2026-34978?
The main impact of CVE-2026-34978 is the potential for path traversal leading to unauthorized file writes outside the designated CacheDir.
Is CVE-2026-34978 easy to exploit?
CVE-2026-34978 can be exploited with minimal technical knowledge, making it a significant risk for affected systems.