CVE-2026-113401 in Firefox
Summary
by MITRE • 10/20/2026
Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 158.0.1.
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Analysis
by VulDB Data Team • 10/20/2026
The identified vulnerability resides within the PDF viewer module of Mozilla Firefox, specifically affecting versions prior to the release of version 158.0.1. As a critical component for rendering document content directly within the browser environment without requiring external plugins or third-party applications, the PDF viewer handles complex parsing logic and memory management operations. The flaw in question is classified as a denial-of-service vulnerability, which indicates that the issue stems from improper handling of specific inputs rather than an arbitrary code execution path. This type of defect typically arises when the application fails to adequately validate input data or manage resource allocation during the processing of malformed PDF files. When a user navigates to a maliciously crafted document designed to exploit this weakness, the parser encounters conditions that trigger abnormal behavior within the rendering engine.
From a technical perspective, denial-of-service vulnerabilities in browser components often involve scenarios where memory limits are exceeded, infinite loops are triggered, or critical system resources become exhausted due to unhandled exceptions. In the context of Firefox's PDF viewer, an attacker could construct a specially crafted PDF file containing specific structural anomalies or malformed objects that cause the rendering engine to enter a state from which it cannot recover gracefully. This might manifest as a complete freeze of the browser tab, excessive consumption of CPU cycles leading to system-wide slowdowns, or a crash of the entire browser process depending on how the operating system handles the faulted application thread. The severity lies in the ease with which such an exploit can be delivered via standard web browsing activities, requiring only that the victim opens the malicious document within their Firefox instance.
The operational impact of this vulnerability is primarily centered around availability and user experience rather than data confidentiality or integrity. A successful exploitation attempt results in the disruption of service for the affected browser session. Users may find themselves unable to continue working with other tabs if the crash affects the main process, or they may face a frozen interface that requires manual intervention through task managers to terminate the unresponsive application. For organizations relying on Firefox for internal document review workflows, such vulnerabilities pose a risk to productivity and can be leveraged in targeted attacks to disrupt operations by forcing employees to restart their workstations repeatedly. While it does not directly lead to remote code execution or data theft, its potential use as part of a broader attack chain cannot be entirely dismissed, particularly if combined with other browser-side exploits that rely on the instability caused by such crashes.
To mitigate this risk, immediate action is required to update all instances of Mozilla Firefox to version 158.0.1 or later, where the underlying parsing logic has been corrected and resource handling improved. Security administrators should ensure that automatic updates are enabled for end-user devices to prevent exposure windows from remaining open after a patch release. Additionally, users can adopt defensive browsing practices such as disabling JavaScript execution in untrusted environments or using containerized profiles for high-risk activities like opening documents downloaded from unknown sources. Monitoring network traffic and endpoint behavior for unusual spikes in resource usage associated with PDF rendering processes may also aid in detecting attempted exploitation of similar vulnerabilities before they cause significant disruption.
This vulnerability aligns with Common Weakness Enumeration categories related to improper input validation and resource management failures, often categorized under CWE-400 or CWE-787 depending on the specific mechanism causing the crash. In terms of adversary tactics, it relates to techniques aimed at disrupting service availability rather than gaining persistence or privilege escalation. The ATT&CK framework categorizes such actions under disruption-focused behaviors where attackers aim to degrade system functionality. By addressing this flaw through timely patching and enforcing secure configuration baselines, organizations can significantly reduce their attack surface regarding browser-based document viewing risks. Continuous monitoring for new CVEs related to core browser components remains essential as these modules are frequent targets due to their complexity and widespread usage across the internet ecosystem.