CVE-2026-107655 in CUPS
Summary
by MITRE • 10/09/2026
A flaw was found in CUPS. When processing embedded job ticket comments within documents, the service improperly handles specific IPP attributes, causing an unhandled null pointer dereference. An unauthenticated attacker permitted to submit jobs to a shared printer queue can send a crafted Internet Printing Protocol (IPP) request to crash the print daemon, resulting in a temporary Denial of Service (DoS) for all printing services.
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Analysis
by VulDB Data Team • 10/09/2026
The Common UNIX Printing System serves as the standard printing subsystem for many Linux distributions and other Unix-like operating systems, acting as an intermediary between applications and physical printers by managing job queues and processing print requests via protocols such as Internet Printing Protocol or IPP. Within this architecture, CUPS processes various attributes embedded within job tickets to configure how documents are rendered and printed. A critical vulnerability has been identified in the handling of these embedded job ticket comments when they contain specific IPP attributes that trigger improper parsing logic. This flaw manifests as an unhandled null pointer dereference, a memory management error where the software attempts to access a memory location at address zero or another invalid base address rather than a valid object reference. Such errors typically occur during runtime execution and result in immediate termination of the affected process unless specific exception handling mechanisms are implemented by the developer, which is notably absent in this instance within CUPS.
The operational impact of this vulnerability centers on service availability for shared printing resources. Because an unauthenticated attacker who has network access to a system running CUPS can submit jobs to a shared printer queue, they possess the necessary vector to exploit this flaw remotely without requiring prior authentication credentials. By crafting and sending a malicious IPP request containing specifically designed job ticket comments with malformed or unexpected attributes, the attacker forces the print daemon into an error state that leads directly to its crash. This results in a temporary Denial of Service condition for all printing services hosted on the affected system. While this does not typically allow for arbitrary code execution or direct data exfiltration due to the nature of null pointer dereferences causing crashes rather than memory corruption exploitable for shellcode, it effectively disrupts business operations by rendering print infrastructure unavailable until the service is manually restarted or automatically recovered if configured with a watchdog process.
From a classification perspective, this vulnerability aligns closely with CWE-476, which defines NULL Pointer Dereference as a software error where a program dereferences a pointer that it expects to be valid but is actually null. This leads to unexpected termination and potential denial of service conditions. In the context of attack tactics, this scenario maps to MITRE ATT&CK technique T1499, Endpoint Denial of Service, specifically under sub-techniques involving resource exhaustion or application crashes via network-based attacks. The attacker leverages their ability to submit jobs as a foothold within the local network perimeter to disrupt critical infrastructure services. This highlights the risk associated with exposing printing daemons directly to untrusted networks without adequate input validation and robust error handling mechanisms in place.
Mitigation strategies for this vulnerability primarily involve applying vendor-provided patches that address the improper pointer initialization or add null checks before dereferencing operations within the IPP attribute parsing logic. Organizations should ensure their CUPS installations are updated to versions where this specific flaw has been remediated by upstream developers. Additionally, network-level controls can be employed to restrict access to printing services; for instance, configuring firewalls to limit connectivity to port 631 and related IPP ports only from trusted subnets or authorized hosts reduces the attack surface significantly. Implementing strict authentication requirements for job submission where feasible further mitigates the risk by ensuring that only verified users can interact with the print daemon, thereby preventing unauthenticated actors from triggering the crash condition even if they have network reachability to the service.