CVE-2026-6770: Firefox Information Disclosure Vulnerability

CVE-2026-6770 Overview

CVE-2026-6770 is an information exposure vulnerability affecting the Storage: IndexedDB component in Mozilla Firefox and Thunderbird. This security flaw exists within the browser's IndexedDB implementation, which is used for client-side storage of significant amounts of structured data. The vulnerability allows potential unauthorized access to sensitive information stored within IndexedDB databases, posing risks to user privacy and data confidentiality.

Critical Impact

This vulnerability in the IndexedDB component could allow attackers to access sensitive data stored in browser databases, potentially exposing user credentials, application data, and other confidential information stored by web applications.

Affected Products

• Mozilla Firefox versions prior to 150
• Mozilla Firefox ESR versions prior to 140.10
• Mozilla Thunderbird versions prior to 150 and 140.10

Discovery Timeline

• 2026-04-21 - CVE-2026-6770 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6770

Vulnerability Analysis

This vulnerability is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). The flaw resides in the IndexedDB storage component, which is a low-level API for client-side storage of significant amounts of structured data, including files and blobs. IndexedDB is commonly used by web applications for offline data storage and caching.

The vulnerability allows potential information leakage from the IndexedDB storage layer. When exploited, an attacker could potentially access data stored by other origins or gain insight into sensitive information that should be protected by the browser's same-origin policy. This represents a breach of the fundamental security boundaries that browsers implement to isolate web content.

Root Cause

The root cause of this vulnerability lies in improper handling of data within the IndexedDB component. The specific implementation flaw allows information to be exposed in scenarios where it should remain protected. This type of vulnerability typically arises from insufficient access controls, improper data isolation, or flawed handling of database operations that bypass security checks.

According to the Mozilla Bug Report #2024220, the issue was identified in the storage handling routines of the IndexedDB implementation.

Attack Vector

The attack vector for CVE-2026-6770 is network-based, meaning the vulnerability can be exploited remotely without requiring prior authentication. An attacker could potentially craft a malicious webpage that, when visited by a victim, exploits the IndexedDB vulnerability to access or leak sensitive information stored by other web applications.

The exploitation does not require user interaction beyond visiting a malicious site, and the attacker does not need any prior privileges on the target system. The vulnerability can result in partial confidentiality impact through information disclosure and partial availability impact.

Detection Methods for CVE-2026-6770

Indicators of Compromise

• Unusual IndexedDB access patterns or queries from unexpected origins
• Abnormal memory access patterns related to browser storage operations
• Browser crash reports indicating IndexedDB-related exceptions
• Unexpected cross-origin data access attempts logged in browser security events

Detection Strategies

• Monitor for anomalous JavaScript execution patterns targeting IndexedDB APIs
• Implement browser telemetry analysis to detect abnormal storage component behavior
• Deploy endpoint detection solutions capable of identifying browser exploitation attempts
• Review browser console logs for IndexedDB-related security exceptions or warnings

Monitoring Recommendations

• Enable enhanced browser logging for storage-related operations in enterprise environments
• Configure SentinelOne agents to monitor for suspicious browser process behavior
• Implement network traffic analysis to detect potential data exfiltration from browser processes
• Set up alerts for unexpected IndexedDB database creation or access patterns

How to Mitigate CVE-2026-6770

Immediate Actions Required

• Update Mozilla Firefox to version 150 or later immediately
• Update Mozilla Firefox ESR to version 140.10 or later
• Update Mozilla Thunderbird to version 150 or 140.10 or later
• Verify all browser instances across the organization are patched

Patch Information

Mozilla has released security patches addressing this vulnerability across multiple product versions. The fixes are documented in the following security advisories:

• Mozilla Security Advisory MFSA-2026-30
• Mozilla Security Advisory MFSA-2026-32
• Mozilla Security Advisory MFSA-2026-33
• Mozilla Security Advisory MFSA-2026-34

Organizations should prioritize updating all affected Mozilla products to the patched versions as soon as possible.

Workarounds

• Restrict access to untrusted websites until patches can be applied
• Consider using browser isolation solutions for high-risk browsing activities
• Implement strict content security policies to limit JavaScript execution from untrusted sources
• Use enterprise browser management tools to enforce automatic updates

# Firefox version verification on Linux/macOS
firefox --version
# Expected output should show version 150 or higher

# Thunderbird version verification
thunderbird --version
# Expected output should show version 150 or 140.10 or higher