CVE-2010-0302 in cups
Summary
by MITRE
Use-after-free vulnerability in the abstract file-descriptor handling interface in the cupsdDoSelect function in scheduler/select.c in the scheduler in cupsd in CUPS before 1.4.4, when kqueue or epoll is used, allows remote attackers to cause a denial of service (daemon crash or hang) via a client disconnection during listing of a large number of print jobs, related to improperly maintaining a reference count. NOTE: some of these details are obtained from third party information. NOTE: this vulnerability exists because of an incomplete fix for CVE-2009-3553.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 05/01/2026
The vulnerability described in CVE-2010-0302 represents a critical use-after-free condition within the Common Unix Printing System (CUPS) scheduler component. This flaw specifically affects the cupsd daemon's abstract file-descriptor handling interface, which is responsible for managing client connections and print job operations. The vulnerability manifests when the system employs kqueue or epoll mechanisms for event handling, which are asynchronous I/O notification mechanisms commonly used in modern Unix-like operating systems to efficiently manage multiple file descriptors. The issue stems from improper reference counting mechanisms within the scheduler's select.c file, particularly in the cupsdDoSelect function that coordinates between different I/O event notification systems.
The technical exploitation of this vulnerability occurs when a remote attacker manipulates the timing of client disconnections during the process of listing large numbers of print jobs. Under normal circumstances, when a client disconnects, the system should properly clean up associated resources and update reference counts to prevent dangling pointers. However, in this case, the reference counting logic fails to properly account for the disconnection event, leading to a situation where freed memory is accessed after it has been deallocated. This use-after-free condition results in undefined behavior that can manifest as daemon crashes, hangs, or complete service unavailability. The vulnerability is particularly dangerous because it can be triggered remotely without authentication requirements, making it an attractive target for denial-of-service attacks against printing services.
The operational impact of CVE-2010-0302 extends beyond simple service disruption to potentially compromise the entire printing infrastructure within affected systems. When the cupsd daemon crashes or hangs, all print jobs queued for processing become inaccessible, effectively cutting off printing capabilities for users and applications that depend on the CUPS service. This vulnerability affects systems running CUPS versions prior to 1.4.4, which represents a significant portion of deployed printing environments given the widespread adoption of CUPS in Unix-like systems. The vulnerability's relationship to CVE-2009-3553 indicates that this was not an isolated issue but rather a recurring problem in the reference counting implementation that was only partially addressed in previous patches. This incomplete fix created a window where the system could still experience memory corruption under specific conditions involving concurrent client connections and resource cleanup operations.
From a cybersecurity perspective, this vulnerability aligns with CWE-416, which describes the use of freed memory condition, and can be mapped to ATT&CK technique T1499.004 for network denial of service attacks. The vulnerability demonstrates how seemingly minor issues in resource management can have significant operational consequences, particularly in critical system components like printing daemons that are often overlooked in security assessments. Organizations using affected CUPS versions should prioritize immediate patching to prevent exploitation, as the vulnerability provides no authentication requirements for triggering the denial-of-service condition. The fix implemented in CUPS 1.4.4 addresses the root cause by properly synchronizing reference counting operations during client disconnection events, ensuring that memory management remains consistent even under high-concurrency scenarios involving large print job lists. Security teams should also monitor for similar patterns in other system components that rely on similar asynchronous I/O handling mechanisms and reference counting approaches to prevent analogous vulnerabilities from emerging in related software systems.