CVE-2026-3845: Mozilla Firefox Buffer Overflow Vulnerability

CVE-2026-3845 Overview

A heap buffer overflow vulnerability has been identified in the Audio/Video: Playback component of Firefox for Android. This memory corruption flaw exists in versions prior to 148.0.2 and can be triggered when processing maliciously crafted audio or video content. The vulnerability allows attackers to potentially corrupt heap memory, which could lead to arbitrary code execution in the context of the browser process.

Critical Impact

Successful exploitation of this heap buffer overflow could allow remote attackers to execute arbitrary code on affected Android devices, potentially compromising user data, credentials, and device security through malicious media content.

Affected Products

• Mozilla Firefox for Android versions prior to 148.0.2

Discovery Timeline

• March 10, 2026 - CVE-2026-3845 published to NVD
• March 12, 2026 - Last updated in NVD database

Technical Details for CVE-2026-3845

Vulnerability Analysis

This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow), which occurs when a program writes data beyond the bounds of an allocated heap buffer. In the context of Firefox for Android's Audio/Video Playback component, the overflow condition arises during media processing operations.

The flaw requires user interaction to exploit, as victims must navigate to a page containing malicious media content or open a crafted media file. Once triggered, the attacker can potentially overwrite adjacent heap memory structures, corrupt function pointers, or manipulate control data to achieve code execution.

Mobile browsers like Firefox for Android are particularly sensitive targets because they process rich media content from potentially untrusted sources while having access to sensitive device capabilities including cameras, microphones, location services, and stored credentials.

Root Cause

The root cause stems from insufficient bounds checking within the Audio/Video playback parsing routines. When processing specially crafted media streams, the component fails to properly validate buffer lengths before writing data, allowing an attacker to overflow the heap-allocated buffer with controlled data. This type of vulnerability typically occurs in complex multimedia codecs where handling of variable-length fields and nested data structures creates opportunities for miscalculated buffer sizes.

Attack Vector

The attack vector for this vulnerability is network-based and requires user interaction. An attacker could exploit this flaw through several methods:

1. Malicious websites - Embedding crafted audio or video content that triggers the overflow when rendered by Firefox for Android
2. Drive-by exploitation - Utilizing advertising networks or compromised legitimate sites to deliver malicious media payloads
3. Social engineering - Sending links to malicious media content via messaging applications or email

The vulnerability is exploited when the victim's browser parses the malicious media content. Technical details regarding the specific exploitation mechanism can be found in the Mozilla Bug Report #2020174.

Detection Methods for CVE-2026-3845

Indicators of Compromise

• Unusual Firefox crashes or unexpected browser restarts on Android devices when accessing media content
• Abnormal memory consumption patterns in the Firefox process during video/audio playback
• Suspicious outbound network connections following media content consumption
• Unexplained application behavior or permission requests after visiting unknown websites

Detection Strategies

• Monitor for Firefox for Android processes exhibiting abnormal memory allocation patterns during media playback
• Implement network-level inspection for malformed media files targeting known vulnerable codecs
• Deploy mobile endpoint detection solutions capable of identifying heap corruption attempts
• Review application logs for repeated crashes in the media playback subsystem

Monitoring Recommendations

• Enable crash reporting for Firefox for Android across managed device fleets to identify potential exploitation attempts
• Implement web traffic filtering to block access to known malicious domains serving exploit content
• Configure mobile device management (MDM) solutions to alert on outdated Firefox installations
• Monitor for unusual process behavior patterns on Android devices that may indicate successful exploitation

How to Mitigate CVE-2026-3845

Immediate Actions Required

• Update Firefox for Android to version 148.0.2 or later immediately across all managed devices
• Advise users to avoid accessing untrusted websites or playing media content from unknown sources until patches are applied
• Consider temporarily restricting autoplay functionality for media content in browser settings
• Implement web filtering policies to block potentially malicious media content at the network perimeter

Patch Information

Mozilla has released Firefox for Android version 148.0.2 which addresses this heap buffer overflow vulnerability. The fix implements proper bounds checking within the Audio/Video Playback component to prevent heap memory corruption. Organizations should prioritize deployment of this update across all Android devices with Firefox installed.

For detailed patch information and release notes, refer to the Mozilla Security Advisory MFSA-2026-19.

Workarounds

• Disable automatic media playback in Firefox for Android settings until the patch can be applied
• Use alternative browsers temporarily for accessing media-rich websites
• Implement network-level content filtering to inspect and sanitize media streams
• Restrict browser permissions on Android devices to limit potential impact of successful exploitation
• Enable Firefox Enhanced Tracking Protection in Strict mode to reduce exposure to potentially malicious content

Organizations should prioritize applying the official patch as workarounds may not fully mitigate the risk of exploitation.