OpenPrinting CUPS up to 2.4.16 on Linux IPP Service /admin/ improper authentication

Summaryinfo

A vulnerability was found in OpenPrinting CUPS up to 2.4.16 on Linux. It has been declared as critical. This affects an unknown part of the file /admin/ of the component IPP Service. Such manipulation leads to improper authentication. This vulnerability is traded as CVE-2026-34990. An attack has to be approached locally. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in OpenPrinting CUPS up to 2.4.16 on Linux. Affected by this issue is some unknown processing of the file /admin/ of the component IPP Service. The manipulation with an unknown input leads to a improper authentication vulnerability. Using CWE to declare the problem leads to CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-34990 since 03/31/2026. The exploitation is known to be easy. Local access is required to approach this attack. Technical details are known, but there is no available exploit.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Printing Software

Vendor

• OpenPrinting

Name

• CUPS

Version

• 2.4.0
• 2.4.1
• 2.4.2
• 2.4.3
• 2.4.4
• 2.4.5
• 2.4.6
• 2.4.7
• 2.4.8
• 2.4.9
• 2.4.10
• 2.4.11
• 2.4.12
• 2.4.13
• 2.4.14
• 2.4.15
• 2.4.16

Website

• Product: https://github.com/OpenPrinting/cups/

CPE 2.3info

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CPE 2.2info

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