CVE-2026-107885 in CUPS
Summary
by MITRE • 10/09/2026
OpenPrinting CUPS through 2.4.20 contains a resource-exhaustion vulnerability in the submission-timeout handling of cupsdCheckJobs(). The scheduler suppresses timeout processing for all pending jobs whenever any client connection has an in-flight Send-Document operation, without matching that connection to the job being examined. A client allowed to reach the IPP service can hold an incomplete HTTP request containing parsed Send-Document headers before operation authorization, preventing unrelated incomplete jobs from expiring. Where Create-Job submission is allowed, incomplete jobs can accumulate until MaxJobs is exhausted and further legitimate print submissions are rejected. The suppression ends when the held connection closes.
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Analysis
by VulDB Data Team • 10/09/2026
The vulnerability identified in OpenPrinting CUPS versions through 2.4.20 represents a significant resource-exhaustion flaw within the scheduler's job management logic, specifically located in the cupsdCheckJobs function responsible for handling submission timeouts. This issue stems from an overly broad suppression mechanism designed to prevent race conditions or inconsistencies during active document transfers. When any client connection is engaged in an in-flight Send-Document operation, the scheduler temporarily halts timeout processing for all pending jobs across the system rather than isolating the check to only those jobs associated with that specific connection. This architectural oversight means that a single active transfer can effectively freeze the expiration logic for every other job waiting in the queue, regardless of whether they are related to the same user or session.
From an operational perspective, this flaw allows malicious actors who have access to the IPP service to manipulate system resources and deny service to legitimate users. By establishing a connection and initiating a Send-Document operation without completing it, an attacker can keep the HTTP request in a state where headers are parsed but authorization has not yet occurred or completed. Because the scheduler suppresses timeout checks for all jobs while this incomplete transfer is active, other print submissions cannot expire as intended. If the system configuration permits Create-Job operations, attackers can exploit this window to submit numerous incomplete jobs that fail to progress due to the suspended timeout logic. These orphaned jobs accumulate in memory and queue structures until they hit the MaxJobs limit defined by the administrator.
Once the maximum job count is reached, CUPS ceases to accept new print submissions from any client, resulting in a complete denial of service for legitimate printing activities. The impact is not limited to immediate resource exhaustion; it also degrades system performance and stability as the scheduler continues to manage an inflated queue of stalled jobs. This behavior aligns with CWE-400, which describes uncontrolled resource consumption, and can be categorized under ATT&CK technique T1496, Resource Hijacking, where attackers consume resources to disrupt availability or degrade service quality for other users on the same system. The vulnerability highlights a critical gap in isolating session-specific state from global scheduler logic during high-level operations like document submission.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The primary defense is to apply vendor-provided patches that update CUPS to version 2.4.30 or later, where the suppression of timeout processing has been corrected to target only jobs associated with the specific connection undergoing a Send-Document operation. In environments where patching is not immediately feasible, administrators should restrict access to the IPP service by enforcing strict authentication requirements before any document transfer operations are initiated. This ensures that incomplete requests cannot linger in an unauthenticated state long enough to trigger the suppression logic. Additionally, configuring lower MaxJobs limits can mitigate the severity of resource exhaustion, though this may impact legitimate high-volume printing workflows and should be balanced against security needs. Regular monitoring of job queue sizes and active connections can also help detect anomalous patterns indicative of exploitation attempts before critical thresholds are reached.