CVE-2026-5859: Google Chrome WebML RCE Vulnerability

CVE-2026-5859 Overview

An integer overflow vulnerability exists in the WebML component of Google Chrome prior to version 147.0.7727.55. This critical security flaw allows a remote attacker to potentially exploit heap corruption through a specially crafted HTML page. The vulnerability is classified with critical severity by the Chromium security team, indicating significant risk to affected users.

Critical Impact

Remote attackers can exploit heap corruption via malicious HTML pages, potentially leading to arbitrary code execution within the browser context.

Affected Products

• Google Chrome prior to version 147.0.7727.55
• Chromium-based browsers using vulnerable WebML implementations
• Desktop platforms running affected Chrome versions

Discovery Timeline

• 2026-04-08 - CVE-2026-5859 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2026-5859

Vulnerability Analysis

This vulnerability stems from an integer overflow condition (CWE-472) within the WebML component of Google Chrome. WebML is the browser's implementation of machine learning APIs that enable web applications to run neural network inference workloads. When processing certain input values, the WebML implementation fails to properly validate integer boundaries, resulting in an overflow condition that corrupts heap memory structures.

The integer overflow occurs during memory allocation calculations, where improperly validated size parameters can wrap around, causing significantly smaller allocations than intended. Subsequent operations then write beyond the allocated buffer boundaries, corrupting adjacent heap metadata and data structures.

Root Cause

The root cause is an integer overflow vulnerability (CWE-472: External Control of Assumed-Immutable Web Parameter) in the WebML component. When handling specially crafted parameters from web content, the code performs arithmetic operations on user-controlled integer values without sufficient bounds checking. This allows attackers to trigger integer wraparound, leading to undersized memory allocations followed by out-of-bounds heap writes.

Attack Vector

The attack vector is network-based, requiring no authentication or user interaction beyond visiting a malicious web page. An attacker can craft a malicious HTML page containing JavaScript that invokes WebML APIs with specially crafted parameters designed to trigger the integer overflow. When a victim navigates to the attacker-controlled page, the browser processes the malicious WebML operations, triggering heap corruption.

The heap corruption can potentially be leveraged for arbitrary code execution within the browser's renderer process. Given Chrome's sandboxing architecture, additional sandbox escape vulnerabilities would typically be required for full system compromise, though the renderer process compromise alone provides significant attack surface.

Detection Methods for CVE-2026-5859

Indicators of Compromise

• Unexpected crashes in Chrome renderer processes with heap corruption signatures
• Browser crash reports indicating faults within WebML-related code paths
• Suspicious network traffic to domains serving heavily obfuscated JavaScript with WebML API calls
• Memory access violations in Chrome processes originating from machine learning inference operations

Detection Strategies

• Monitor browser crash telemetry for patterns indicating heap corruption in WebML components
• Deploy network-based detection for HTML pages containing suspicious WebML API invocations with abnormal parameter values
• Utilize endpoint detection and response (EDR) solutions to identify anomalous Chrome process behavior
• Implement browser version auditing to identify systems running vulnerable Chrome versions

Monitoring Recommendations

• Enable Chrome's built-in crash reporting to capture and analyze heap corruption events
• Configure SentinelOne agents to monitor for suspicious Chrome process memory operations
• Audit enterprise browser deployments to ensure timely updates to version 147.0.7727.55 or later
• Monitor security advisories from the Google Chrome Releases Blog

How to Mitigate CVE-2026-5859

Immediate Actions Required

• Update Google Chrome to version 147.0.7727.55 or later immediately
• Enable automatic browser updates to ensure timely security patches
• Review and restrict access to untrusted websites in enterprise environments
• Consider deploying browser isolation solutions for high-risk browsing activities

Patch Information

Google has released a security update addressing this vulnerability in Chrome version 147.0.7727.55. The patch corrects the integer overflow condition in the WebML component by implementing proper bounds validation on user-controlled parameters before memory allocation calculations.

For detailed patch information, refer to the Google Chrome Stable Channel Update. Additional technical details may be available in the Chromium Issue Tracker once the disclosure embargo period has concluded.

Workarounds

• Disable WebML functionality via Chrome flags (chrome://flags) if the feature is not required, pending patch deployment
• Implement network-level filtering to block access to known malicious domains
• Deploy content security policies to restrict JavaScript execution from untrusted sources
• Consider using enterprise browser management to enforce immediate updates across the organization

# Verify Chrome version and trigger update check
# On Windows
"C:\Program Files\Google\Chrome\Application\chrome.exe" --version

# On macOS
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --version

# On Linux
google-chrome --version

# Force update check by navigating to:
# chrome://settings/help