CVE-2026-109769 in Firefox
Summary
by MITRE • 10/13/2026
Information disclosure in the Networking: Cache component. This vulnerability was fixed in Firefox 158.
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Analysis
by VulDB Data Team • 10/13/2026
The identified security issue resides within the networking cache subsystem of Mozilla Firefox, specifically affecting version prior to 158. The core technical flaw involves an improper handling of cached network resources which leads to unintended information disclosure. In a typical web browsing scenario, the browser's caching mechanism stores copies of responses from HTTP requests to improve performance and reduce bandwidth usage. However, in this specific instance, the implementation failed to correctly isolate or sanitize data associated with these cache entries under certain conditions. This oversight allows sensitive metadata or content that should remain private to be exposed to unauthorized contexts, potentially including other tabs, extensions, or malicious scripts operating within a compromised page context.
From a technical perspective, vulnerabilities in caching layers often stem from race conditions, improper access control checks on cached objects, or the failure to clear specific headers and body data when transitioning between different security domains. The lack of strict separation ensures that information intended for one origin might leak into another where it does not belong. This type of flaw is particularly dangerous because cache entries are frequently reused across multiple requests without re-evaluating their sensitivity level against the current request's context. Consequently, an attacker could potentially exploit this by crafting specific network requests or manipulating browser state to trigger the retrieval of cached data that contains private user information, authentication tokens, or internal application logic details.
The operational impact of such a vulnerability is significant for end-users and enterprise environments alike. Information disclosure can lead to session hijacking if sensitive cookies or headers are leaked. It may also facilitate further attacks by revealing server-side structures, database query patterns, or configuration details that aid in crafting more sophisticated exploits. For organizations relying on Firefox as their primary browser, this vulnerability represents a risk to data confidentiality and integrity. The exposure of internal network information could compromise the security posture of intranet applications or sensitive web services accessed through the browser.
To mitigate these risks, immediate action is required to update the Mozilla Firefox installation to version 158 or later, where this flaw has been addressed by the development team. Users should ensure that automatic updates are enabled to receive future patches promptly. In enterprise settings, IT administrators must verify deployment policies to guarantee all endpoints are updated within a reasonable timeframe after patch release. Additionally, implementing strict Content Security Policy headers and disabling unnecessary caching for sensitive pages can provide an additional layer of defense against similar vulnerabilities in the future. Regular security audits and monitoring for unusual network activity patterns can also help detect potential exploitation attempts before significant damage occurs.
This vulnerability aligns with Common Weakness Enumeration category CWE-200, which covers Information Exposure. It is relevant to MITRE ATT&CK technique T1537, specifically related to communication through a different channel or medium than expected, although the primary vector here is local browser state manipulation rather than external network exfiltration directly. Understanding these classifications helps in mapping the risk to broader security frameworks and ensuring that mitigation strategies are comprehensive and aligned with industry best practices for web application security and browser hardening.