CVE-2026-74935 in Firefox
Summary
by MITRE • 08/18/2026
Privilege escalation in the DOM: Networking component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/18/2026
The disclosed vulnerability represents a critical privilege escalation flaw within the Document Object Model networking component of Mozilla Firefox browsers. This security defect allows an attacker to bypass intended access controls by exploiting inconsistencies in how the browser handles network requests initiated through DOM APIs versus those triggered by standard user interactions or internal processes. The core technical issue stems from insufficient validation checks during the execution context of certain scripting operations, specifically when these operations interact with cross-origin resources or sensitive network endpoints. By carefully crafting malicious web content that leverages specific JavaScript methods to manipulate request headers or origins, an adversary can trick the browser into treating a potentially untrusted resource as if it were originating from a trusted domain or possessing higher system privileges than intended. This misalignment in permission evaluation creates a pathway for unauthorized data access or state manipulation that violates the same-origin policy, which is fundamental to web security architecture.
From an operational perspective, this vulnerability poses significant risks to user privacy and data integrity. An attacker could potentially exfiltrate sensitive information such as authentication tokens, session cookies, or personal identifiable information stored in local storage by forcing the browser to send these credentials with requests that appear legitimate due to the manipulated context. Furthermore, if the affected component interacts with internal network services or APIs that are not typically exposed to web content, this flaw could allow for lateral movement within a corporate environment where Firefox is deployed as the primary browsing tool. The impact extends beyond simple data theft; it undermines the trust model of the browser by allowing low-privilege scripts to achieve high-privilege actions, effectively breaking the sandbox isolation that protects users from malicious websites.
The remediation strategy involves updating to patched versions of Mozilla Firefox and its Extended Support Release branches. Specifically, organizations must ensure deployment of Firefox version 154 or later, as well as Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1. These updates contain code changes that enforce stricter validation rules within the DOM networking layer, ensuring that origin checks are performed consistently regardless of how a request is initiated. Administrators should prioritize patching across all endpoints to mitigate the risk of exploitation in enterprise environments where sensitive data processing occurs via web applications. Additionally, implementing Content Security Policy headers can provide an additional layer of defense by restricting which sources scripts can load and execute from, thereby reducing the attack surface even if similar vulnerabilities are discovered in future updates.
This vulnerability aligns with Common Weakness Enumeration category CWE-269, which addresses Improper Privilege Management, as it involves a failure to correctly enforce authority levels during resource access. In terms of offensive security frameworks, this flaw facilitates techniques associated with ATT&CK T1059, specifically command and script interpretation through JavaScript, by allowing malicious scripts to perform actions that would otherwise be blocked due to insufficient privileges. The exploitation vector typically falls under web-based attacks where the initial entry point is a compromised or malicious website designed to trigger the specific DOM interaction sequence required to escalate privileges. Continuous monitoring for anomalous network traffic patterns originating from browser processes can aid in detecting potential attempts to exploit this weakness before full compromise occurs, although reliance on timely patching remains the most effective mitigation strategy given the nature of client-side vulnerabilities.