CVE-2026-5733: Mozilla Firefox Buffer Overflow Vulnerability

CVE-2026-5733 Overview

CVE-2026-5733 is a boundary condition vulnerability affecting the Graphics: WebGPU component in Mozilla Firefox and Thunderbird. This flaw stems from improper boundary checks (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer), which could allow an attacker to cause memory corruption when processing specially crafted WebGPU content. Successful exploitation requires user interaction, such as visiting a malicious website or opening a crafted document.

Critical Impact

This vulnerability could allow remote attackers to execute arbitrary code or cause denial of service through memory corruption in the WebGPU graphics component, potentially leading to full system compromise.

Affected Products

• Mozilla Firefox versions prior to 149.0.2
• Mozilla Thunderbird versions prior to 149.0.2

Discovery Timeline

• 2026-04-07 - CVE-2026-5733 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2026-5733

Vulnerability Analysis

This vulnerability exists in the WebGPU implementation within Mozilla Firefox's graphics subsystem. WebGPU is a modern graphics API designed to provide high-performance access to GPU capabilities for web applications. The flaw involves incorrect boundary conditions that fail to properly validate memory operations, potentially allowing out-of-bounds memory access.

The attack requires network access and user interaction—typically convincing a victim to visit a malicious webpage containing specially crafted WebGPU content. Once triggered, the improper boundary validation can lead to memory corruption, which attackers may leverage to achieve arbitrary code execution within the browser's context or cause the application to crash.

Root Cause

The root cause is improper restriction of operations within the bounds of a memory buffer (CWE-119) in the WebGPU graphics component. Boundary conditions are not correctly validated when processing WebGPU operations, allowing memory operations to exceed allocated buffer boundaries. This class of vulnerability typically occurs when array indices or pointer arithmetic are not properly checked against buffer limits.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker would need to:

1. Create a malicious webpage containing specially crafted WebGPU shader code or GPU buffer operations
2. Lure a victim to visit the malicious page using a vulnerable Firefox or Thunderbird version
3. The WebGPU component processes the malicious content, triggering the boundary condition error
4. Memory corruption occurs, potentially allowing code execution in the context of the browser process

The vulnerability mechanism involves improper boundary validation in WebGPU memory operations. When processing GPU buffer data or shader operations, the affected code fails to properly check that memory accesses remain within allocated boundaries. This can lead to out-of-bounds reads or writes, corrupting adjacent memory regions. For detailed technical information, refer to the Mozilla Bug Report #2022554 and Mozilla Security Advisory MFSA-2026-25.

Detection Methods for CVE-2026-5733

Indicators of Compromise

• Unexpected Firefox or Thunderbird crashes, particularly when visiting WebGPU-enabled websites
• Unusual memory consumption patterns in browser processes
• Crash reports indicating memory corruption in graphics or WebGPU-related modules
• Suspicious outbound network connections following browser anomalies

Detection Strategies

• Monitor for Firefox/Thunderbird versions below 149.0.2 in software inventory systems
• Implement browser crash analysis to identify patterns consistent with memory corruption exploits
• Deploy endpoint detection rules targeting abnormal WebGPU API usage patterns
• Use network monitoring to identify traffic to known malicious domains serving WebGPU exploits

Monitoring Recommendations

• Enable enhanced crash reporting for Mozilla products to capture memory corruption events
• Configure SIEM alerts for repeated browser crashes from the same user or system
• Monitor for suspicious JavaScript or WebGPU shader code in web traffic
• Track browser version compliance across the organization to identify unpatched systems

How to Mitigate CVE-2026-5733

Immediate Actions Required

• Update Mozilla Firefox to version 149.0.2 or later immediately
• Update Mozilla Thunderbird to version 149.0.2 or later immediately
• Consider temporarily disabling WebGPU in Firefox via about:config by setting dom.webgpu.enabled to false if immediate patching is not possible
• Review browser security policies and ensure automatic updates are enabled

Patch Information

Mozilla has released security patches addressing this vulnerability in Firefox 149.0.2 and Thunderbird 149.0.2. The patches correct the boundary condition checks in the WebGPU component to properly validate memory operations. Organizations should prioritize deploying these updates through their patch management systems. For detailed patch information, see Mozilla Security Advisory MFSA-2026-25 and Mozilla Security Advisory MFSA-2026-28.

Workarounds

• Disable WebGPU functionality via Firefox configuration settings until patching is complete
• Implement web content filtering to block access to untrusted sites that may exploit this vulnerability
• Use browser isolation technologies to contain potential exploitation attempts
• Deploy network-level protections to filter known malicious WebGPU payloads

# Disable WebGPU in Firefox via user.js or policies
# Add to user.js in Firefox profile directory:
user_pref("dom.webgpu.enabled", false);

# Or deploy via enterprise policies (policies.json):
# {
#   "policies": {
#     "Preferences": {
#       "dom.webgpu.enabled": false
#     }
#   }
# }