CVE-2026-5867: Google Chrome WebML Buffer Overflow Flaw

CVE-2026-5867 Overview

A heap buffer overflow vulnerability has been identified in the WebML component of Google Chrome prior to version 147.0.7727.55. This memory corruption flaw allows a remote attacker to potentially obtain sensitive information from process memory by enticing a victim to visit a specially crafted HTML page. The vulnerability was assigned a High severity rating by the Chromium security team.

Critical Impact

Successful exploitation enables remote attackers to read sensitive data from Chrome's process memory, potentially exposing credentials, session tokens, or other confidential information through a malicious web page.

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-2026-5867 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2026-5867

Vulnerability Analysis

This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow). The flaw exists within Chrome's WebML implementation, which provides machine learning capabilities for web applications. When processing malformed input through a crafted HTML page, the WebML component fails to properly validate buffer boundaries, resulting in a heap buffer overflow condition.

The vulnerability allows an attacker to read beyond the intended memory boundaries, potentially accessing sensitive data stored in adjacent heap memory regions. This type of out-of-bounds read can expose process memory contents including cached credentials, authentication tokens, encryption keys, or other confidential data that may reside in the browser's memory space.

Root Cause

The root cause stems from improper bounds checking in the WebML component's memory handling routines. When processing specially crafted machine learning model data or related WebML API calls, the component allocates a heap buffer but fails to validate that subsequent read operations remain within the allocated boundaries. This allows controlled out-of-bounds memory access when an attacker provides malicious input through a crafted web page.

Attack Vector

The attack is remotely exploitable through user interaction. An attacker must convince a victim to visit a malicious website containing a specially crafted HTML page that leverages the WebML API. When the victim's browser processes this page:

1. The malicious page invokes WebML functionality with crafted parameters
2. The vulnerable code path triggers the heap buffer overflow
3. Memory contents beyond the allocated buffer are read
4. Sensitive information from process memory can be exfiltrated to the attacker

No authentication is required, and the attack can be delivered through common vectors such as phishing links, malicious advertisements, or compromised websites.

Detection Methods for CVE-2026-5867

Indicators of Compromise

• Unusual WebML API calls or excessive machine learning operations from untrusted web pages
• Browser crash dumps or error logs indicating heap corruption in Chrome's renderer process
• Network traffic exfiltrating encoded data to external domains following visits to suspicious pages
• Memory access violations or segmentation faults in Chrome's WebML-related components

Detection Strategies

• Monitor Chrome browser version deployments across the enterprise and flag systems running versions prior to 147.0.7727.55
• Implement web content filtering to block access to known malicious domains exploiting this vulnerability
• Deploy endpoint detection and response (EDR) solutions capable of identifying memory corruption exploitation attempts
• Analyze browser telemetry for anomalous WebML API usage patterns

Monitoring Recommendations

• Enable Chrome crash reporting and monitor for crashes related to WebML or machine learning components
• Configure SIEM alerts for multiple browser crashes occurring across endpoints within short timeframes
• Review web proxy logs for connections to suspicious domains following Chrome crash events
• Implement browser isolation for high-risk browsing activities to contain potential exploitation

How to Mitigate CVE-2026-5867

Immediate Actions Required

• Update Google Chrome to version 147.0.7727.55 or later immediately across all systems
• Enable automatic Chrome updates to ensure timely deployment of future security patches
• Consider temporarily restricting access to untrusted websites until patches are deployed
• Review and update browser security policies to limit exposure to web-based threats

Patch Information

Google has addressed this vulnerability in Chrome version 147.0.7727.55. Organizations should prioritize updating all Chrome installations to this version or later. Additional details about the security update are available in the Google Chrome Update Blog. Technical details regarding the specific issue can be found in the Chromium Issue Tracker Entry.

Workarounds

• Disable WebML functionality if not required for business operations (may require Chrome flags or enterprise policy)
• Implement browser isolation solutions to execute untrusted web content in sandboxed environments
• Use web filtering to block access to categories of websites commonly used for drive-by attacks
• Consider deploying alternative browsers temporarily for sensitive activities until Chrome can be updated

# Verify Chrome version and force update check
# Windows PowerShell - Check Chrome version
Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\chrome.exe" | Select-Object "(Default)"

# Linux - Check Chrome version
google-chrome --version

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

# Force Chrome update (requires restart)
# Navigate to chrome://settings/help to trigger update check