CVE-2026-6756: Mozilla Firefox Auth Bypass Vulnerability

CVE-2026-6756 Overview

CVE-2026-6756 is a mitigation bypass vulnerability affecting Firefox for Android. This security flaw allows attackers to circumvent security protections implemented in the mobile browser, potentially enabling unauthorized modifications to browser behavior or data. The vulnerability was addressed in Firefox version 150.

Critical Impact

This mitigation bypass vulnerability could allow attackers to undermine security controls in Firefox for Android, potentially leading to integrity compromise of browser operations without requiring user interaction.

Affected Products

• Mozilla Firefox for Android (versions prior to 150)

Discovery Timeline

• 2026-04-21 - CVE-2026-6756 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6756

Vulnerability Analysis

This vulnerability is classified under CWE-200 (Information Exposure), indicating that the mitigation bypass may involve improper handling of sensitive information or security boundaries within Firefox for Android. The flaw enables attackers to bypass existing security mitigations that are designed to protect users from malicious activities.

The network-based attack vector means this vulnerability can be exploited remotely without requiring any privileges or user interaction. The primary impact is on integrity, allowing attackers to potentially modify data or browser behavior without authorization.

Root Cause

The root cause stems from insufficient enforcement of security mitigations in Firefox for Android. This could involve improper validation of security boundaries, allowing attackers to circumvent protective mechanisms that should prevent unauthorized access or modifications.

Attack Vector

The vulnerability is exploitable over the network with low complexity. An attacker could craft malicious content or network requests that exploit the mitigation bypass to compromise the integrity of the browser session. Since no user interaction is required, this attack could be executed silently when a user visits a malicious website or encounters crafted network traffic.

Technical details are available in the Mozilla Bug Report #1992585 and the Mozilla Security Advisory MFSA-2026-30.

Detection Methods for CVE-2026-6756

Indicators of Compromise

• Unusual network requests originating from Firefox for Android that bypass expected security controls
• Unexpected modifications to browser data or settings without user action
• Anomalous behavior in Firefox for Android that suggests security mitigations are not functioning correctly

Detection Strategies

• Monitor for Firefox for Android versions prior to 150 in your mobile device fleet
• Implement mobile device management (MDM) solutions to track browser versions across enterprise devices
• Review network traffic for patterns associated with exploitation attempts targeting Firefox mobile browsers

Monitoring Recommendations

• Enable centralized logging for mobile browser activity where possible
• Configure alerts for outdated Firefox for Android versions in your environment
• Monitor Mozilla security advisories for updates related to CVE-2026-6756

How to Mitigate CVE-2026-6756

Immediate Actions Required

• Update Firefox for Android to version 150 or later immediately
• Audit all Android devices in your environment to identify vulnerable Firefox installations
• Consider temporarily restricting access to untrusted websites until patches are applied

Patch Information

Mozilla has released a security update addressing this vulnerability in Firefox version 150. The patch information and details are available in the Mozilla Security Advisory MFSA-2026-30. Users and administrators should update to the latest version through the Google Play Store or their organization's app deployment mechanism.

Workarounds

• Use alternative browsers on Android devices until Firefox can be updated
• Implement network-level filtering to block access to known malicious domains
• Enable strict security policies through MDM solutions to limit browser exposure to untrusted content

# Verify Firefox for Android version via ADB
adb shell dumpsys package org.mozilla.firefox | grep versionName
# Expected output for patched version: versionName=150.0 or higher