CVE-2026-6775: Mozilla Firefox Buffer Overflow Vulnerability

CVE-2026-6775 Overview

CVE-2026-6775 is a boundary condition vulnerability in the WebRTC component of Mozilla Firefox and Thunderbird. This flaw arises from incorrect boundary conditions (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer), potentially allowing an attacker to read memory contents beyond intended boundaries. The vulnerability is network-exploitable and requires no user interaction or privileges to trigger.

Critical Impact

Information disclosure via out-of-bounds memory access in WebRTC component could leak sensitive data from affected browser sessions.

Affected Products

• Mozilla Firefox (versions prior to 150)
• Mozilla Thunderbird (versions prior to 150)

Discovery Timeline

• 2026-04-21 - CVE-2026-6775 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6775

Vulnerability Analysis

This vulnerability stems from improper handling of boundary conditions within the WebRTC (Web Real-Time Communication) component. WebRTC enables real-time communication capabilities in browsers for audio, video, and data sharing. The flaw allows network-based attackers to potentially access memory contents that should be restricted, leading to information disclosure.

The vulnerability can be exploited remotely without requiring authentication or user interaction. While the impact is limited to confidentiality concerns (no integrity or availability impact), successful exploitation could expose sensitive information processed by the browser.

Root Cause

The root cause is classified as CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer. The WebRTC component fails to properly validate or enforce boundary conditions when processing certain operations, allowing read access beyond intended memory boundaries. This type of vulnerability typically occurs when array indices or pointer arithmetic calculations don't account for edge cases.

Attack Vector

The attack vector is network-based, meaning an attacker can exploit this vulnerability remotely without physical or local access to the target system. The attack complexity is low, requiring no special privileges or user interaction. A malicious actor could craft specific WebRTC communications or set up a malicious website that triggers the vulnerable code path when a victim visits the page or establishes a WebRTC connection.

The vulnerability mechanism involves improper boundary checking in the WebRTC processing logic. For detailed technical information, refer to Mozilla Bug Report #2021768 and the associated security advisories.

Detection Methods for CVE-2026-6775

Indicators of Compromise

• Unusual WebRTC connection patterns or traffic to untrusted domains
• Abnormal memory access patterns in browser processes related to WebRTC operations
• Unexpected browser crashes or instability during WebRTC sessions

Detection Strategies

• Monitor for Firefox or Thunderbird versions prior to version 150 in your environment
• Deploy network monitoring to detect anomalous WebRTC traffic patterns
• Use endpoint detection solutions to identify exploitation attempts targeting browser components

Monitoring Recommendations

• Enable enhanced logging for browser-based network communications
• Monitor for unexpected data exfiltration patterns from browser processes
• Track browser version deployments across the organization to identify unpatched instances

How to Mitigate CVE-2026-6775

Immediate Actions Required

• Update Mozilla Firefox to version 150 or later immediately
• Update Mozilla Thunderbird to version 150 or later immediately
• Review and restrict WebRTC permissions in browser security policies if updates cannot be applied immediately

Patch Information

Mozilla has released security patches addressing this vulnerability in Firefox 150 and Thunderbird 150. Security advisories with patch details are available:

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

Organizations should prioritize deploying these updates through their standard patch management processes.

Workarounds

• Disable WebRTC functionality in browser settings if the feature is not required for business operations
• Use browser policies to restrict WebRTC connections to trusted domains only
• Consider implementing network-level controls to limit WebRTC traffic until patches can be applied

# Firefox WebRTC configuration (about:config)
# Set the following preference to disable WebRTC if not needed:
# media.peerconnection.enabled = false