CVE-2026-5858: Google Chrome WebML Buffer Overflow Flaw

CVE-2026-5858 Overview

A heap buffer overflow vulnerability has been identified in the WebML component of Google Chrome. This critical memory corruption flaw exists in versions prior to 147.0.7727.55 and allows remote attackers to potentially execute arbitrary code on affected systems. The vulnerability can be triggered when a user visits a maliciously crafted HTML page, making it exploitable through standard web browsing activities.

Critical Impact

Remote attackers can achieve arbitrary code execution by exploiting a heap buffer overflow in Chrome's WebML implementation through specially crafted web content.

Affected Products

• Google Chrome versions prior to 147.0.7727.55
• Chromium-based browsers using vulnerable WebML implementations
• Desktop platforms running affected Chrome versions (Windows, macOS, Linux)

Discovery Timeline

• 2026-04-08 - CVE-2026-5858 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2026-5858

Vulnerability Analysis

This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow), a severe memory corruption issue occurring within the WebML component of Google Chrome. WebML is the browser's implementation of machine learning inference capabilities, which processes neural network models and tensor operations within web applications.

The heap buffer overflow occurs when WebML improperly handles memory boundaries during tensor operations or model parsing. When processing malicious input data through a crafted HTML page, the vulnerable code writes beyond the allocated heap buffer, corrupting adjacent memory structures. This memory corruption can be leveraged by attackers to achieve arbitrary code execution within the context of the Chrome renderer process.

The Chromium security team has rated this vulnerability as Critical severity, indicating significant exploitability and impact potential. Successful exploitation requires no user interaction beyond visiting a malicious webpage, making it particularly dangerous for drive-by attack scenarios.

Root Cause

The root cause stems from insufficient bounds checking within the WebML component when processing input data. During tensor operations or model inference tasks, the code fails to properly validate buffer sizes against the actual data being processed. This oversight allows an attacker to supply oversized or malformed data that triggers a write operation past the end of an allocated heap buffer, leading to heap metadata corruption and potential control flow hijacking.

Attack Vector

The attack is remotely exploitable through the network by delivering malicious content via a crafted HTML page. An attacker can host or inject malicious WebML-triggering content on a website. When a victim navigates to the page using a vulnerable Chrome version, the malicious payload is processed by the WebML component, triggering the heap buffer overflow.

The exploitation chain typically involves:

1. Victim visits attacker-controlled or compromised webpage
2. Malicious HTML/JavaScript invokes WebML APIs with crafted input
3. WebML processes malformed data, causing heap overflow
4. Attacker-controlled data overwrites critical heap structures
5. Code execution is achieved through heap exploitation techniques

Due to Chrome's sandboxing architecture, successful exploitation of this vulnerability in the renderer process may require chaining with additional sandbox escape vulnerabilities to achieve full system compromise.

Detection Methods for CVE-2026-5858

Indicators of Compromise

• Unusual Chrome renderer process crashes or unexpected terminations during web browsing
• Memory access violations or heap corruption errors logged in system event logs
• Suspicious JavaScript activity involving WebML or machine learning APIs on visited pages
• Abnormal network traffic patterns from Chrome processes following webpage visits

Detection Strategies

• Monitor for Chrome crash reports specifically mentioning WebML component failures
• Implement web filtering to identify and block known malicious domains serving exploit payloads
• Deploy endpoint detection rules targeting anomalous memory operations in browser processes
• Analyze JavaScript execution patterns for suspicious WebML API invocations

Monitoring Recommendations

• Enable enhanced crash reporting in Chrome enterprise deployments for vulnerability impact assessment
• Configure security information and event management (SIEM) systems to correlate browser crashes with recent navigation history
• Implement network traffic inspection for suspicious HTML/JavaScript patterns targeting WebML functionality
• Monitor for updates to the Chromium Issue Tracker Entry for additional threat intelligence

How to Mitigate CVE-2026-5858

Immediate Actions Required

• Update Google Chrome to version 147.0.7727.55 or later immediately across all endpoints
• Enable automatic updates in Chrome to ensure timely delivery of security patches
• Review and restrict access to untrusted websites through web filtering policies
• Consider disabling WebML features if not required for business operations until patching is complete

Patch Information

Google has released a security update addressing this vulnerability in Chrome version 147.0.7727.55. Organizations should prioritize deployment of this update across all managed Chrome installations. The official release announcement is available in the Google Chrome Stable Update blog post.

For enterprise environments, use Chrome's managed browser policies to enforce version requirements and automatic update schedules. Verify patch deployment through browser version auditing tools.

Workarounds

• Implement strict web filtering to block access to untrusted or unknown websites
• Consider using browser isolation technologies to contain potential exploitation attempts
• Deploy Content Security Policy (CSP) headers on internal web applications to limit script execution capabilities
• Temporarily disable experimental WebML features through Chrome flags if patching is delayed

# Verify Chrome version meets minimum patched version
google-chrome --version
# Expected output: Google Chrome 147.0.7727.55 or higher

# Force Chrome update check (Linux)
sudo apt update && sudo apt upgrade google-chrome-stable

# Enterprise deployment verification
# Check Chrome policy for automatic updates
chrome://policy