CVE-2026-4714: Mozilla Firefox Buffer Overflow Vulnerability

CVE-2026-4714 Overview

CVE-2026-4714 is a boundary condition vulnerability affecting the Audio/Video component in Mozilla Firefox and Thunderbird. The flaw stems from incorrect boundary conditions (CWE-754: Improper Check for Unusual or Exceptional Conditions) that can be exploited remotely over a network connection without requiring user interaction or authentication. This vulnerability primarily impacts the availability of affected applications.

Critical Impact

Remote attackers can exploit incorrect boundary conditions in Firefox's Audio/Video component to cause denial of service, potentially crashing the browser or disrupting media processing functionality.

Affected Products

• Mozilla Firefox versions prior to 149
• Mozilla Firefox ESR versions prior to 140.9
• Mozilla Thunderbird versions prior to 149 and 140.9

Discovery Timeline

• 2026-03-24 - CVE-2026-4714 published to NVD
• 2026-03-25 - Last updated in NVD database

Technical Details for CVE-2026-4714

Vulnerability Analysis

This vulnerability exists within the Audio/Video processing component of Mozilla Firefox and related products. The flaw involves incorrect boundary conditions that fail to properly validate or handle exceptional conditions during media processing operations.

The vulnerability is remotely exploitable without requiring any privileges or user interaction, making it accessible to unauthenticated attackers across network boundaries. While the confidentiality and integrity of affected systems remain unaffected, successful exploitation can result in complete disruption of service availability.

The vulnerability is classified under CWE-754 (Improper Check for Unusual or Exceptional Conditions), indicating that the affected code does not adequately check for boundary conditions that could lead to unexpected behavior when processing audio/video content.

Root Cause

The root cause lies in improper boundary condition checking within the Audio/Video component. When processing media content, the component fails to properly validate certain boundary conditions, which can lead to exceptional states that the application cannot handle gracefully. This improper exception handling allows attackers to trigger conditions that disrupt normal operation.

Attack Vector

The attack vector is network-based with low complexity requirements. An attacker can craft malicious media content or manipulate audio/video streams to trigger the incorrect boundary conditions. Since no user interaction is required, the vulnerability can potentially be exploited through:

• Maliciously crafted web pages containing specially prepared audio/video elements
• Manipulated media files that trigger boundary condition failures when processed
• Streaming content designed to exploit the improper exception handling

The vulnerability does not require authentication, and the scope remains unchanged, meaning the impact is limited to the vulnerable component itself. For detailed technical information, refer to the Mozilla Bug Report #2018126 and the associated security advisories.

Detection Methods for CVE-2026-4714

Indicators of Compromise

• Unexpected Firefox or Thunderbird crashes during audio/video playback
• Application crashes when visiting specific websites containing media content
• Repeated browser process terminations correlating with media processing activities

Detection Strategies

• Monitor system logs for Firefox and Thunderbird crash events, particularly those associated with media component failures
• Implement endpoint detection rules to identify abnormal browser termination patterns
• Deploy SentinelOne agents to detect and correlate crash events with network activity involving untrusted media sources

Monitoring Recommendations

• Enable crash reporting and analyze crash dumps for signatures matching Audio/Video component failures
• Monitor network traffic for suspicious media file downloads from untrusted sources
• Implement application performance monitoring to detect service degradation patterns in browser instances

How to Mitigate CVE-2026-4714

Immediate Actions Required

• Update Mozilla Firefox to version 149 or later immediately
• Update Mozilla Firefox ESR to version 140.9 or later
• Update Mozilla Thunderbird to version 149 or 140.9 (ESR) or later
• Restrict access to untrusted websites that may serve malicious media content until patches are applied

Patch Information

Mozilla has released security patches addressing this vulnerability. Organizations should apply the following updates:

• Firefox 149: Contains the fix for this boundary condition vulnerability
• Firefox ESR 140.9: Extended Support Release with the security fix
• Thunderbird 149 / 140.9: Patched versions for Thunderbird users

For complete patch details, refer to the official Mozilla Security Advisories:

• Mozilla Security Advisory MFSA-2026-20
• Mozilla Security Advisory MFSA-2026-22
• Mozilla Security Advisory MFSA-2026-23
• Mozilla Security Advisory MFSA-2026-24

Workarounds

• Disable automatic media playback in browser settings until the patch can be applied
• Use content blocking extensions to prevent loading of media content from untrusted sources
• Consider using network-level filtering to block potentially malicious media content from reaching vulnerable endpoints

# Firefox configuration to disable autoplay (about:config settings)
# Set media.autoplay.default to 5 to block all autoplay
user_pref("media.autoplay.default", 5);
# Block audio and video autoplay
user_pref("media.autoplay.blocking_policy", 2);