CVE-2025-4082: Mozilla Firefox Privilege Escalation Flaw

CVE-2025-4082 Overview

CVE-2025-4082 is an out-of-bounds read vulnerability affecting Mozilla Firefox and Thunderbird. The flaw exists in the WebGL shader processing component, where modification of specific WebGL shader attributes could trigger an out-of-bounds memory read operation. When chained with other vulnerabilities, this security issue could potentially be leveraged to escalate privileges on affected systems.

Critical Impact

This vulnerability enables out-of-bounds memory read operations through malicious WebGL shader manipulation, which could expose sensitive memory contents and facilitate privilege escalation when combined with additional exploits. Note that this bug only affects Thunderbird for macOS—other versions of Thunderbird are unaffected.

Affected Products

• Mozilla Firefox versions prior to 138
• Mozilla Firefox ESR versions prior to 128.10 and 115.23
• Mozilla Thunderbird versions prior to 138 and 128.10 (macOS only for Thunderbird)

Discovery Timeline

• April 29, 2025 - CVE-2025-4082 published to NVD
• November 3, 2025 - Last updated in NVD database

Technical Details for CVE-2025-4082

Vulnerability Analysis

This vulnerability (CWE-125: Out-of-bounds Read) resides in the WebGL rendering subsystem of Mozilla Firefox and Thunderbird. WebGL is a JavaScript API for rendering interactive 2D and 3D graphics within web browsers, and it relies on shader programs written in GLSL (OpenGL Shading Language) to process graphics data on the GPU.

The flaw occurs during the processing of WebGL shader attributes. When specific shader attributes are modified in a particular manner, the application fails to properly validate memory access boundaries, resulting in an out-of-bounds read condition. This can allow an attacker to read memory beyond the allocated buffer, potentially exposing sensitive information stored in adjacent memory regions.

While the immediate impact is information disclosure through unauthorized memory access, the vulnerability becomes more severe when chained with other security flaws. An attacker could potentially use the leaked memory information to bypass security mechanisms such as ASLR (Address Space Layout Randomization), facilitating further exploitation that could lead to privilege escalation.

Root Cause

The root cause of CVE-2025-4082 is improper bounds checking in the WebGL shader attribute processing code. When shader attributes are modified, the code fails to validate that memory access operations remain within allocated buffer boundaries. This allows reads to occur beyond the intended memory region, constituting an out-of-bounds read vulnerability. The issue is classified under CWE-125 (Out-of-bounds Read), a common memory safety vulnerability that occurs when software reads data past the end of an intended buffer.

Attack Vector

The attack vector for this vulnerability is network-based, requiring no user interaction and no prior authentication. An attacker could exploit this vulnerability by:

1. Crafting a malicious web page containing WebGL content with specially modified shader attributes
2. Convincing a victim to visit the malicious page using a vulnerable version of Firefox or Thunderbird (for email HTML content)
3. The malicious WebGL shader code executes in the browser context, triggering the out-of-bounds read
4. Memory contents beyond the intended buffer are exposed to the attacker
5. The leaked memory information could then be used in conjunction with other vulnerabilities to escalate privileges

The vulnerability demonstrates the potential for graphics subsystem vulnerabilities to impact browser security. When visiting a malicious website or viewing malicious email content in Thunderbird, the crafted WebGL shaders could trigger the memory read issue. For detailed technical information, refer to the Mozilla Bug Report #1937097.

Detection Methods for CVE-2025-4082

Indicators of Compromise

• Unusual WebGL activity or shader compilation errors in browser logs
• Abnormal memory access patterns associated with graphics rendering processes
• Suspicious web pages containing obfuscated WebGL shader code
• Browser crashes or unexpected behavior following visits to untrusted websites

Detection Strategies

• Monitor browser processes for anomalous memory read operations outside expected boundaries
• Implement content security policies that restrict WebGL usage to trusted domains
• Deploy endpoint detection solutions capable of identifying exploit attempts targeting browser graphics subsystems
• Review browser console logs for WebGL-related errors or warnings that may indicate exploitation attempts

Monitoring Recommendations

• Enable enhanced logging for WebGL operations in enterprise browser deployments
• Utilize SentinelOne's behavioral AI engine to detect anomalous browser process activity
• Monitor network traffic for connections to known malicious domains hosting WebGL exploits
• Implement browser telemetry collection to identify potential exploitation patterns across your environment

How to Mitigate CVE-2025-4082

Immediate Actions Required

• Update Mozilla Firefox to version 138 or later immediately
• Update Mozilla Firefox ESR to version 128.10 or 115.23 or later
• Update Mozilla Thunderbird to version 138 or 128.10 or later (especially on macOS)
• Consider temporarily disabling WebGL on high-value systems until patches can be applied

Patch Information

Mozilla has released security patches addressing this vulnerability across multiple product versions. The following security advisories provide detailed patch information:

• Mozilla Security Advisory MFSA-2025-28
• Mozilla Security Advisory MFSA-2025-29
• Mozilla Security Advisory MFSA-2025-30
• Mozilla Security Advisory MFSA-2025-31
• Mozilla Security Advisory MFSA-2025-32

Debian users should also review the Debian LTS Announcement for distribution-specific patch information.

Workarounds

• Disable WebGL in Firefox by navigating to about:config and setting webgl.disabled to true
• Implement network-level filtering to block access to known malicious domains
• Use browser isolation solutions to contain potential exploitation attempts
• Restrict browser usage on critical systems to trusted, verified websites only

# Disable WebGL in Firefox via user.js configuration
# Add to user.js in Firefox profile directory
echo 'user_pref("webgl.disabled", true);' >> user.js

# Verify WebGL is disabled by visiting about:support in Firefox
# and checking the "WebGL 1 Driver Renderer" field shows "Blocked"