CVE-2026-6752: Mozilla Firefox Buffer Overflow Vulnerability

CVE-2026-6752 Overview

CVE-2026-6752 is a boundary condition error vulnerability affecting the WebRTC component in Mozilla Firefox and Thunderbird. The vulnerability stems from incorrect boundary conditions that can lead to improper buffer access during WebRTC media processing operations. This flaw falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which encompasses various memory safety issues that can compromise application security.

WebRTC (Web Real-Time Communication) is a critical browser component that enables real-time audio, video, and data communication directly between browsers. Due to the complexity of media processing and the network-exposed nature of WebRTC, vulnerabilities in this component present significant security concerns as they can be triggered through malicious web content without requiring user interaction beyond visiting a webpage.

Critical Impact

Network-accessible boundary condition flaw in WebRTC may allow remote attackers to compromise confidentiality, integrity, and availability of affected Mozilla products through malicious web content.

Affected Products

• Mozilla Firefox versions prior to 150
• Mozilla Firefox ESR versions prior to 115.35 and 140.10
• Mozilla Thunderbird versions prior to 150 and 140.10

Discovery Timeline

• April 21, 2026 - CVE-2026-6752 published to NVD
• April 22, 2026 - Last updated in NVD database

Technical Details for CVE-2026-6752

Vulnerability Analysis

The vulnerability exists within the WebRTC component's handling of boundary conditions during media stream processing. WebRTC implementations involve complex buffer management for handling audio and video data in real-time, and incorrect boundary validation can result in out-of-bounds memory operations.

When the WebRTC component processes certain media streams or session descriptions, the boundary checking logic fails to properly validate input parameters before memory operations. This can allow an attacker to craft malicious WebRTC session data or media streams that trigger memory access outside intended buffer boundaries.

The network-accessible nature of this vulnerability is particularly concerning, as exploitation requires no user privileges and can be triggered simply by visiting a malicious webpage that initiates a WebRTC session. The low attack complexity combined with network accessibility makes this vulnerability an attractive target for drive-by exploitation scenarios.

Root Cause

The root cause of CVE-2026-6752 is improper boundary condition validation in the WebRTC component's memory management routines. When processing WebRTC-related data structures, the code fails to adequately verify that array indices or buffer offsets remain within valid bounds before performing read or write operations.

This type of flaw (CWE-119) occurs when software performs operations on a memory buffer but can read from or write to memory locations outside the intended buffer boundaries. In the context of WebRTC, this could occur during:

• Processing of SDP (Session Description Protocol) parameters
• Handling of RTP/RTCP media packets
• Management of peer connection state data
• Audio or video codec buffer operations

Attack Vector

The attack vector for CVE-2026-6752 is network-based, requiring no user authentication or special privileges. An attacker could exploit this vulnerability by:

1. Hosting malicious content: Creating a webpage that initiates a WebRTC peer connection with carefully crafted parameters designed to trigger the boundary condition error
2. Malicious media streams: Sending specially crafted media stream data through an established WebRTC connection
3. Session manipulation: Crafting malicious SDP offers or answers that exploit the boundary checking flaw

The vulnerability mechanism involves improper bounds validation in WebRTC buffer operations. When the component receives malformed input data, it may perform memory operations that exceed buffer boundaries, potentially leading to information disclosure, memory corruption, or application crashes. Technical details can be found in the Mozilla Bugzilla Report.

Detection Methods for CVE-2026-6752

Indicators of Compromise

• Unexpected crashes in Firefox or Thunderbird processes, particularly firefox.exe, thunderbird.exe, or content process children, with crash signatures indicating WebRTC component faults
• Abnormal memory allocation patterns or heap corruption errors in browser processes during web browsing sessions
• Process crash dumps showing stack traces involving WebRTC-related functions or libraries
• Unusual network traffic patterns indicating WebRTC session establishment to suspicious or unknown STUN/TURN servers

Detection Strategies

• Monitor for Mozilla browser process crashes with exception codes indicating memory access violations or heap corruption
• Implement network monitoring to detect WebRTC signaling traffic (SDP exchanges) containing anomalous or malformed parameters
• Deploy endpoint detection rules that flag repeated browser crashes associated with specific websites or domains
• Utilize browser telemetry and crash reporting to identify patterns consistent with exploitation attempts

Monitoring Recommendations

• Enable Mozilla crash reporting to aggregate and analyze crash data for patterns indicating exploitation
• Configure SentinelOne agents to monitor Firefox and Thunderbird processes for suspicious memory operations and unexpected terminations
• Implement DNS monitoring to detect connections to known malicious WebRTC infrastructure
• Review application logs for repeated WebRTC initialization failures or unusual error patterns

How to Mitigate CVE-2026-6752

Immediate Actions Required

• Update Mozilla Firefox to version 150 or later immediately across all systems
• Update Mozilla Firefox ESR to version 115.35 or 140.10 or later
• Update Mozilla Thunderbird to version 150 or 140.10 or later
• Prioritize updates on systems with high-value data or elevated network exposure

Patch Information

Mozilla has released security patches addressing this vulnerability in the following versions:

For detailed patch information, refer to the official Mozilla Security Advisories:

• MFSA-2026-30
• MFSA-2026-31
• MFSA-2026-32
• MFSA-2026-33
• MFSA-2026-34

Workarounds

• Disable WebRTC functionality in Firefox by navigating to about:config and setting media.peerconnection.enabled to false until patching is complete
• Use network-level controls to block WebRTC STUN/TURN traffic if WebRTC functionality is not required in your environment
• Consider temporary deployment of alternative browsers for users requiring WebRTC functionality until patches can be applied
• Implement strict site isolation and process sandboxing to limit potential impact of exploitation

# Firefox WebRTC Disable Configuration (user.js)
// Add to Firefox profile user.js to disable WebRTC
user_pref("media.peerconnection.enabled", false);
user_pref("media.peerconnection.ice.default_address_only", true);
user_pref("media.peerconnection.identity.enabled", false);