CVE-2026-109744 in Firefox
Summary
by MITRE • 10/13/2026
Other issue in the DOM: File 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 flaw resides within the Document Object Model implementation of Mozilla Firefox, specifically affecting the file input component used for handling user-initiated file selections on web pages. While the provided description is brief, vulnerabilities in DOM-based file components typically involve improper validation or sanitization of file paths and metadata before they are exposed to JavaScript contexts or passed to underlying operating system APIs. In many such cases, attackers may exploit inconsistencies between how the browser parses local file references and how it exposes them via standard web interfaces like HTML5 File API objects. This can lead to scenarios where sensitive information is inadvertently disclosed or where the application logic assumes a level of isolation that does not exist due to path traversal ambiguities or incorrect handling of symbolic links on certain operating systems.
From a technical perspective, this issue likely stems from a failure in boundary checking or type enforcement within the internal structures managing file inputs. When a user selects a local file through an HTML form element with type=file, the browser creates a File object that contains properties such as name, size, and lastModifiedDate. If these properties are not strictly validated against expected formats or if path normalization is performed incorrectly, it may allow for information disclosure regarding the absolute path of files on the user's local machine. This can be particularly dangerous in enterprise environments where sensitive documents reside in predictable directory structures, allowing an attacker to infer file locations even without direct read access, thereby facilitating further targeted attacks such as social engineering or precise payload delivery if combined with other vulnerabilities like cross-site scripting.
The operational impact of this vulnerability centers on the potential for unauthorized information disclosure and privacy violations. An attacker hosting a malicious webpage could potentially extract sensitive local file paths from users who interact with compromised forms, especially in scenarios where the browser's security model is bypassed or confused by malformed inputs. Although modern browsers employ strict same-origin policies and sandboxing to limit damage, flaws in core components like the DOM can erode these defenses by leaking metadata that aids reconnaissance. For end-users, this means their local file system structure could be partially mapped without explicit permission beyond the initial file selection action if they are tricked into interacting with a malicious form field. The risk is heightened for users who frequently upload sensitive documents to web applications, as leaked path information can correlate with known vulnerabilities in server-side software or reveal the presence of specific security tools installed on the machine.
Mitigation strategies primarily involve applying the vendor-provided patches immediately upon availability. Mozilla has addressed this issue in Firefox version 158 and Firefox Extended Support Release (ESR) version 153.5, which contain code corrections to ensure proper validation and sanitization of file component inputs within the DOM. Organizations should enforce automated update policies to ensure all client machines are running these patched versions or later. Additionally, developers integrating web applications that rely on complex file handling mechanisms should implement strict server-side validation for any metadata received from clients, ensuring that path information is not trusted blindly even if it originates from a supposedly secure browser context. Security awareness training can also help users recognize suspicious form interactions that request unnecessary local file access, reducing the attack surface through behavioral controls while technical patches are propagated across infrastructure.
This vulnerability aligns with common weakness categories such as CWE-20 Improper Input Validation and potentially CWE-798 Use of Hard-coded Credentials if it involves accessing default paths, though primarily it relates to information leakage via improper handling of user-supplied data in a privileged context. In terms of the MITRE ATT&CK framework, this could be associated with T1530 Data from Local System which describes techniques for collecting files from local storage on compromised systems or endpoints. By addressing these flaws at the browser engine level, Mozilla reduces the efficacy of automated reconnaissance tools that rely on DOM-based information gathering to map out victim environments prior to executing more destructive exploits.