CVE-2025-66287: WebKitGTK DoS Vulnerability

CVE-2025-66287 Overview

A buffer overflow vulnerability has been identified in WebKitGTK that allows attackers to cause an unexpected process crash through improper memory handling when processing maliciously crafted web content. This flaw, classified as CWE-120 (Buffer Copy without Checking Size of Input), occurs when the WebKitGTK rendering engine fails to properly validate the size of input during buffer copy operations, leading to memory corruption that can be triggered remotely through malicious web pages.

Critical Impact

Successful exploitation of this vulnerability can lead to arbitrary code execution with the privileges of the affected application, potentially allowing attackers to gain full control of systems running vulnerable WebKitGTK versions through specially crafted web content.

Affected Products

• WebKitGTK (all vulnerable versions prior to patched releases)
• Red Hat Enterprise Linux systems with WebKitGTK packages
• Linux distributions using WebKitGTK as a web rendering component

Discovery Timeline

• December 4, 2025 - CVE-2025-66287 published to NVD
• April 15, 2026 - Last updated in NVD database

Technical Details for CVE-2025-66287

Vulnerability Analysis

This vulnerability stems from improper memory handling within WebKitGTK's content processing routines. When the browser engine processes certain malicious web content, it fails to adequately validate input boundaries during buffer copy operations. The flaw allows an attacker to craft web content that triggers a buffer overflow condition, corrupting adjacent memory regions and potentially hijacking program execution flow.

The vulnerability requires user interaction, meaning a victim must navigate to or be redirected to attacker-controlled web content for exploitation to occur. Once triggered, the memory corruption can result in an immediate process crash (denial of service) or, in more sophisticated attacks, could potentially be leveraged for arbitrary code execution.

Root Cause

The root cause is classified as CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow'). This occurs when the WebKitGTK code performs buffer copy operations without properly validating that the source data fits within the destination buffer's allocated size. When processing maliciously crafted web content, oversized input data can overflow the buffer boundaries, corrupting stack or heap memory and potentially overwriting critical data structures or return addresses.

Attack Vector

The attack vector is network-based, requiring an attacker to lure a victim to a malicious webpage or inject malicious content into a legitimate site. The exploitation flow involves:

1. Attacker hosts or injects malicious web content designed to trigger the buffer overflow
2. Victim browses to the malicious content using an application leveraging WebKitGTK
3. WebKitGTK attempts to process the malformed content
4. Buffer overflow occurs due to missing size validation
5. Memory corruption leads to process crash or potential code execution

The vulnerability does not require any special privileges and exploits standard web browsing behavior, making it particularly dangerous for users of GNOME Web (Epiphany) and other GTK-based applications that utilize WebKitGTK for rendering web content.

Detection Methods for CVE-2025-66287

Indicators of Compromise

• Unexpected crashes of WebKitGTK-based applications (GNOME Web, Evolution, etc.)
• Core dumps or crash reports indicating memory corruption in libwebkitgtk libraries
• Suspicious network traffic directing users to unusual or newly registered domains
• Memory access violations logged in system journals related to WebKit processes

Detection Strategies

• Monitor system logs for repeated crashes of WebKitGTK-dependent applications
• Implement web filtering to block access to known malicious domains serving exploit content
• Deploy endpoint detection solutions capable of identifying memory corruption attack patterns
• Use application-level crash analysis tools to identify suspicious crash patterns

Monitoring Recommendations

• Enable crash reporting and analysis for all WebKitGTK-based applications
• Monitor network traffic for unusual outbound connections following browser activity
• Implement web content inspection at the network perimeter to identify potential exploit payloads
• Review system journals (journalctl) for WebKit-related crash events

How to Mitigate CVE-2025-66287

Immediate Actions Required

• Update WebKitGTK packages to the latest patched versions immediately
• Apply Red Hat Enterprise Linux security updates if running affected RHEL versions
• Restrict access to untrusted websites until patches can be applied
• Consider temporarily disabling JavaScript in WebKitGTK-based browsers as a workaround

Patch Information

Multiple security advisories have been released addressing this vulnerability:

• Red Hat Security Advisory RHSA-2025:22789
• Red Hat Security Advisory RHSA-2025:22790
• Red Hat Security Advisory RHSA-2025:23110
• Red Hat Security Advisory RHSA-2025:23433
• Red Hat Security Advisory RHSA-2025:23434
• WebKitGTK Security Advisory WSA-2025-0009

For detailed technical information, refer to Red Hat CVE Analysis CVE-2025-66287 and Red Hat Bug Report #2418857.

Workarounds

• Use alternative browsers that do not rely on WebKitGTK until patches are applied
• Implement strict content security policies on internal web applications
• Enable browser isolation technologies where available
• Use network-level web filtering to restrict access to untrusted content

# Update WebKitGTK on Red Hat-based systems
sudo dnf update webkitgtk4 webkit2gtk3

# Update WebKitGTK on Debian/Ubuntu-based systems
sudo apt update && sudo apt upgrade libwebkit2gtk-4.0-37

# Verify installed WebKitGTK version
rpm -q webkitgtk4 webkit2gtk3  # RHEL/Fedora
dpkg -l libwebkit2gtk*          # Debian/Ubuntu