CVE-2024-10941: Mozilla Firefox DOS Vulnerability

CVE-2024-10941 Overview

CVE-2024-10941 is a denial-of-service vulnerability in Mozilla Firefox versions prior to 126. A malicious website can embed an iframe pointing to a malformed Uniform Resource Identifier (URI), causing the browser to crash. Mozilla classifies the crash as non-exploitable, meaning it does not lead to memory corruption or arbitrary code execution. The flaw is tracked under [CWE-86] and NVD-CWE-Other and is documented in Mozilla Security Advisory MFSA-2024-21. Exploitation requires only that a user visit or load content from an attacker-controlled page.

Critical Impact
Remote attackers can crash Firefox browsers through a crafted iframe URI, disrupting user sessions and causing availability loss without requiring authentication.

Affected Products

Mozilla Firefox versions earlier than 126
Any application embedding the affected Gecko engine builds
Downstream distributions shipping Firefox < 126

Discovery Timeline

2024-11-06 - CVE-2024-10941 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-10941

Vulnerability Analysis

The vulnerability resides in Firefox's handling of iframe elements that reference malformed URIs. When Gecko attempts to parse and load the embedded resource, the malformed input triggers an unrecoverable condition that terminates the content process. The result is a browser crash that interrupts the user's session and any unsaved activity across open tabs sharing the same process.

Mozilla's advisory classifies the crash as non-exploitable. This means the condition does not permit memory corruption, type confusion, or code execution primitives that would allow an attacker to pivot beyond denial of service. The impact is limited to availability. The issue is referenced in Mozilla Bug Report #1880879 and Mozilla Bug Report #1887614.

User interaction is required because the victim must load the attacker's page or a page embedding attacker-controlled iframe content. Advertising networks, compromised sites, and HTML email previews that render remote content are plausible delivery channels.

Root Cause

The root cause is improper handling of malformed URI input during iframe resource loading in Gecko. Instead of rejecting the malformed input and continuing execution, the parser enters a state that forces process termination. The weakness is categorized as [CWE-86] (Improper Neutralization of Invalid Characters in Identifiers).

Attack Vector

An attacker hosts or injects HTML containing an iframe whose src attribute references a malformed URI. When a Firefox user before version 126 loads the page, the browser attempts to resolve the iframe and crashes. No authentication or elevated privileges are required. The vulnerability is network-exploitable through any delivery vector that renders attacker-controlled HTML.

Technical reproduction details are available in the referenced Mozilla Bugzilla entries. No public proof-of-concept exploit is listed in Exploit-DB, and the CVE is not present on the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2024-10941

Indicators of Compromise

Repeated Firefox content-process crashes recorded in about:crashes or forwarded to the Mozilla Crash Reporter
Browser telemetry showing unexpected tab or process termination following navigation to untrusted sites
Web proxy logs showing requests to pages containing iframes with malformed src URI schemes

Detection Strategies

Correlate endpoint crash telemetry for firefox.exe or firefox-bin with concurrent browsing activity to identify crash-inducing URLs
Inspect HTTP response bodies traversing web gateways for iframe elements referencing malformed or syntactically invalid URIs
Monitor browser version inventory to flag endpoints still running Firefox builds earlier than 126

Monitoring Recommendations

Centralize browser crash reports in your SIEM for trend analysis across the fleet
Alert when the installed Firefox version on managed endpoints falls below 126
Track outbound requests to newly registered or low-reputation domains serving HTML with embedded iframes

How to Mitigate CVE-2024-10941

Immediate Actions Required

Upgrade all Firefox installations to version 126 or later across managed and user-managed endpoints
Audit enterprise browser deployment packages, MDM profiles, and Group Policy configurations to confirm the patched build is distributed
Advise users to avoid visiting untrusted sites until the upgrade is complete

Patch Information

Mozilla addressed CVE-2024-10941 in Firefox 126. Refer to Mozilla Security Advisory MFSA-2024-21 for the full list of fixes and release notes. Enterprise administrators should deploy the Firefox 126 ESR-equivalent or later build appropriate for their environment.

Workarounds

Disable iframe loading from untrusted origins using Content Security Policy (CSP) frame-src directives on hosted applications
Deploy enterprise policies that restrict Firefox usage to vetted sites until patching is complete
Route browser traffic through a web filtering proxy that strips or sanitizes malformed iframe URIs

bash

# Verify installed Firefox version on Linux endpoints
firefox --version

# Example Ansible task to enforce minimum Firefox version
- name: Ensure Firefox is at least version 126
  package:
    name: firefox
    state: latest