CVE-2026-24869: Firefox Use-After-Free Vulnerability

CVE-2026-24869 Overview

CVE-2026-24869 is a use-after-free vulnerability discovered in the Layout: Scrolling and Overflow component of Mozilla Firefox. This memory corruption flaw occurs when the browser improperly handles memory during scrolling and overflow layout operations, potentially allowing attackers to execute arbitrary code or cause unexpected behavior in the browser.

Use-after-free vulnerabilities are particularly dangerous in browser contexts as they can be triggered through malicious web content, requiring only that a user visit a crafted webpage to potentially be exploited.

Critical Impact

A use-after-free vulnerability in Firefox's layout engine could allow remote attackers to achieve arbitrary code execution or information disclosure by enticing users to visit malicious web pages.

Affected Products

• Mozilla Firefox versions prior to 147.0.2

Discovery Timeline

• 2026-01-27 - CVE-2026-24869 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2026-24869

Vulnerability Analysis

This use-after-free vulnerability exists within Firefox's Layout: Scrolling and Overflow component, which is responsible for handling how content is rendered when it exceeds container boundaries and requires scrolling functionality. Use-after-free conditions occur when a program continues to reference memory after it has been freed, leading to undefined behavior.

In browser rendering engines, the layout component maintains complex object relationships between DOM elements, style information, and rendering frames. During scrolling operations, these objects may be invalidated or freed while other parts of the code still hold references to them. An attacker can craft malicious HTML and CSS that triggers specific scrolling and overflow conditions, causing the browser to access freed memory.

The vulnerability can be exploited remotely over the network, requiring user interaction (visiting a malicious webpage). Successful exploitation could result in unauthorized access to sensitive information or modification of browser state, compromising both confidentiality and integrity.

Root Cause

The root cause of this vulnerability is improper memory management within Firefox's layout engine during scrolling and overflow operations. When the browser processes certain combinations of scrollable content and overflow handling, memory objects may be freed while dangling pointers still reference them. Subsequent access to these freed objects through the dangling pointers results in the use-after-free condition.

This type of flaw typically arises from complex object lifecycle management in browser rendering pipelines, where asynchronous layout updates, garbage collection, and event handling can create race conditions or unexpected object destruction sequences.

Attack Vector

The attack vector for CVE-2026-24869 is network-based, requiring user interaction. An attacker would need to:

1. Create a malicious webpage containing specially crafted HTML and CSS designed to trigger the vulnerable scrolling and overflow behavior
2. Entice a victim to visit the malicious page using a vulnerable Firefox version
3. The malicious content triggers the use-after-free condition during layout processing
4. The attacker can potentially leverage the memory corruption to read sensitive data or achieve code execution

For detailed technical information about this vulnerability, refer to the Mozilla Bug Report #2008698 and the Mozilla Security Advisory MFSA-2026-06.

Detection Methods for CVE-2026-24869

Indicators of Compromise

• Unexpected Firefox crashes, particularly during page scrolling or when loading content-heavy pages with complex overflow layouts
• Browser memory corruption errors or access violations in crash logs referencing layout or scroll-related functions
• Unusual network connections or process spawning from Firefox following visits to unknown websites
• Firefox processes exhibiting abnormal memory usage patterns

Detection Strategies

• Monitor endpoint detection systems for memory corruption indicators in Firefox processes
• Deploy network security solutions to detect and block known malicious domains serving exploit payloads
• Implement browser telemetry monitoring to identify unusual crash patterns across the organization
• Use SentinelOne's behavioral AI to detect post-exploitation activities following browser compromise

Monitoring Recommendations

• Enable crash reporting in Firefox and monitor for crashes in layout-related components
• Review browser logs for unusual page loading behavior or rendering errors
• Monitor for signs of lateral movement or data exfiltration following potential browser exploitation
• Configure security tools to alert on Firefox processes spawning unexpected child processes

How to Mitigate CVE-2026-24869

Immediate Actions Required

• Update Mozilla Firefox to version 147.0.2 or later immediately across all systems
• Implement browser isolation solutions for high-risk users until patches can be deployed
• Restrict access to untrusted websites through web filtering where possible
• Enable automatic updates for Firefox to ensure timely security patch deployment

Patch Information

Mozilla has addressed this vulnerability in Firefox version 147.0.2. Organizations should immediately deploy this update to all systems running affected Firefox versions. The fix addresses the memory management issue in the Layout: Scrolling and Overflow component to prevent the use-after-free condition.

For official patch information and additional details, see the Mozilla Security Advisory MFSA-2026-06.

Workarounds

• Use browser isolation technology to contain potential exploits until patching is complete
• Consider temporarily using an alternative browser for high-risk browsing activities
• Implement strict content security policies and web filtering to limit exposure to potentially malicious content
• Enable Firefox's Enhanced Tracking Protection in Strict mode to reduce attack surface from third-party content

# Verify Firefox version on Linux/macOS systems
firefox --version

# Update Firefox on Debian/Ubuntu systems
sudo apt update && sudo apt install firefox

# Update Firefox on RHEL/Fedora systems  
sudo dnf update firefox