CVE-2026-109781 in Firefox
Summary
by MITRE • 10/13/2026
Denial-of-service in the Printing: Output component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5.
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Analysis
by VulDB Data Team • 10/13/2026
The identified security issue resides within the printing subsystem of Mozilla Firefox, specifically affecting the output processing components responsible for rendering documents to physical or virtual printers. As a denial-of-service vulnerability, this flaw does not compromise the confidentiality or integrity of user data but rather impacts the availability of the browser application itself. The root cause typically involves improper handling of specific print-related inputs, such as malformed PostScript commands, excessively large page descriptions, or edge-case scenarios in the rendering engine that trigger unhandled exceptions or infinite loops within the printing pipeline. When a maliciously crafted webpage triggers this condition during the print preview or actual printing process, it can cause the browser to become unresponsive, crash, or consume excessive system resources such as memory and CPU cycles until the application is forcibly terminated by the user or operating system.
This type of vulnerability aligns with Common Weakness Enumeration (CWE) categories related to resource exhaustion and improper input validation, particularly CWE-400: Uncontrolled Resource Consumption and CWE-20: Improper Input Validation. From a threat actor perspective, this flaw could be leveraged in social engineering attacks where an adversary convinces a victim to visit a malicious website that automatically initiates the printing process or opens the print dialog with hostile content. While less severe than remote code execution vulnerabilities, denial-of-service flaws can disrupt productivity and serve as a vector for more complex attacks if combined with other browser exploits. The impact is primarily localized to the user's session stability rather than systemic compromise of the underlying operating system or network infrastructure.
The vulnerability has been addressed in Firefox version 158 and Firefox Extended Support Release (ESR) version 153.5 through rigorous code reviews and patching efforts that enhance input sanitization and error handling within the printing output module. These updates ensure that malformed print requests are gracefully rejected or handled without causing system instability. To maintain security posture, users must upgrade to these patched versions immediately if they have not already done so. Organizations relying on Firefox ESR should verify their deployment pipelines include this specific update cycle. Additionally, administrators can mitigate residual risks by configuring browser policies to restrict automatic printing capabilities and disabling unnecessary print-related features for standard user profiles, thereby reducing the attack surface available to potential exploiters attempting to trigger resource exhaustion conditions.