CVE-2026-34990: openprinting cups Improper Authentication

Vulnerability summary

CVE-2026-34990 is a high (CVSS 7.8) Improper Authentication vulnerability in openprinting cups. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 7.3% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 03-04-2026
   PublishedVulnerability first disclosed.
2. 06-04-2026
   Last modifiedVulnerability information updated.

Description

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.16 and prior, a local unprivileged user can coerce cupsd into authenticating to an attacker-controlled localhost IPP service with a reusable Authorization: Local ... token. That token is enough to drive /admin/ requests on localhost, and the attacker can combine CUPS-Create-Local-Printer with printer-is-shared=true to persist a file:///... queue even though the normal FileDevice policy rejects such URIs. Printing to that queue gives an arbitrary root file overwrite; the PoC below uses that primitive to drop a sudoers fragment and demonstrate root command execution. At time of publication, there are no publicly available patches.

• CWE-287Improper AuthenticationWhen an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.