CUPS’s scheduler performs two case‑insensitive comparisons on usernames extracted from client requests. These comparisons occur outside the main authentication path, in the printer ACL validation and private‑attribute filtering logic. Because the comparison is case‑insensitive, an attacker who supplies a username differing only by case from an authorized user can bypass the intended access controls and gain unauthorized access to the printer’s resources or private attributes. This weakness is classified as CWE‑178 and results in an authentication bypass that could allow a user to perform operations reserved for other users.

The flaw affects Red Hat distributions that ship with CUPS, including Red Hat Enterprise Linux 6 through 10, Red Hat Hardened Images, and Red Hat OpenShift Container Platform 4. Versions of CUPS bundled in those products are susceptible unless the vendor has applied the fix. The Red Hat Hummingbird image (cpe:/a:redhat:hummingbird:1) is also impacted. The vulnerability is present in all affected releases where the default CUPS configuration is used.

The CVSS score of 3 indicates low severity; the EPSS score is not available and the flaw is not listed in CISA’s KEV catalog. The likely attack vector is remote, through the network service that CUPS exposes for print job submission and attribute queries. An attacker who can send a crafted request that supplies a case‑variant username can trigger the unsanitized comparison, bypassing authentication checks without requiring elevated privileges. The absence of a high exploit probability and the low CVSS suggest that the flaw would be exploited only in environments where the CUPS service is exposed to untrusted networks or where the privileged access controls have been relaxed.