CVE-2026-5919: Google Chrome WebSockets SOP Bypass Flaw

CVE-2026-5919 Overview

CVE-2026-5919 is an Improper Input Validation vulnerability affecting the WebSockets implementation in Google Chrome. The flaw stems from insufficient validation of untrusted input, which allows a remote attacker who has already compromised the renderer process to bypass the same origin policy through a crafted HTML page. This vulnerability requires user interaction and prior renderer compromise, limiting its standalone exploitation potential but making it a valuable component in chained attacks.

Critical Impact

Attackers with renderer process access can bypass same origin policy protections, potentially allowing unauthorized cross-origin data access and manipulation through malicious WebSocket connections.

Affected Products

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

Discovery Timeline

• April 8, 2026 - CVE CVE-2026-5919 published to NVD
• April 9, 2026 - Last updated in NVD database

Technical Details for CVE-2026-5919

Vulnerability Analysis

This vulnerability exists within Google Chrome's WebSocket handling code, specifically in how untrusted input is validated during WebSocket connection establishment and message processing. The same origin policy (SOP) is a critical browser security mechanism that restricts how documents or scripts loaded from one origin can interact with resources from other origins.

When the renderer process is compromised, an attacker can craft malicious HTML content that exploits the insufficient input validation in the WebSocket implementation. This allows the attacker to bypass SOP restrictions, potentially enabling unauthorized access to data from different origins that should otherwise be protected.

The vulnerability is classified under CWE-20 (Improper Input Validation), indicating that the WebSocket code fails to properly validate, filter, or sanitize input before processing it. This type of flaw can lead to security boundary violations when malicious input is crafted to exploit the validation gap.

Root Cause

The root cause of CVE-2026-5919 lies in the WebSocket implementation's failure to adequately validate origin-related input parameters. When processing WebSocket connection requests or messages, the affected Chrome versions do not properly verify that the input conforms to expected security constraints, particularly around origin enforcement. This allows crafted input to manipulate the origin checking logic, effectively bypassing same origin policy protections.

Attack Vector

The attack requires a multi-stage exploitation approach:

1. Renderer Compromise: The attacker must first compromise Chrome's renderer process through a separate vulnerability or attack vector
2. Crafted HTML Delivery: Once the renderer is compromised, the attacker delivers a specially crafted HTML page to the victim
3. WebSocket Manipulation: The malicious page leverages the input validation weakness in WebSocket handling to bypass SOP restrictions
4. Cross-Origin Access: With SOP bypassed, the attacker can perform unauthorized cross-origin operations

The vulnerability is exploited over the network and requires user interaction (visiting the malicious page). The attack impacts integrity by allowing unauthorized cross-origin modifications.

The vulnerability mechanism involves crafting malicious WebSocket connection parameters that exploit the insufficient input validation. When processed by the vulnerable Chrome version, these parameters allow the attacker to bypass origin checks that would normally prevent cross-origin WebSocket communications. For detailed technical information, refer to the Chromium Issue Tracker.

Detection Methods for CVE-2026-5919

Indicators of Compromise

• Unusual WebSocket connection patterns originating from compromised renderer processes
• Cross-origin WebSocket communications that bypass normal SOP restrictions
• Anomalous network traffic patterns involving WebSocket protocol with unexpected origin headers
• Evidence of renderer process compromise preceding WebSocket-based attacks

Detection Strategies

• Monitor browser telemetry for signs of renderer process compromise as a precursor indicator
• Implement network-level monitoring to detect anomalous WebSocket connection patterns
• Deploy endpoint detection solutions capable of identifying browser exploitation attempts
• Analyze web server logs for requests containing crafted HTML payloads targeting this vulnerability

Monitoring Recommendations

• Enable Chrome's built-in security logging to capture WebSocket-related security events
• Implement SentinelOne's behavioral detection to identify post-exploitation activity in browser processes
• Monitor for unexpected cross-origin data exfiltration following browser sessions
• Track Chrome version deployment across the organization to identify vulnerable instances

How to Mitigate CVE-2026-5919

Immediate Actions Required

• Update Google Chrome to version 147.0.7727.55 or later immediately
• Verify all Chromium-based browsers in the environment are updated to patched versions
• Review security policies to ensure automatic browser updates are enabled
• Conduct asset inventory to identify all systems running vulnerable Chrome versions

Patch Information

Google has addressed this vulnerability in Chrome version 147.0.7727.55. The fix implements proper input validation for WebSocket connections, ensuring that origin-related parameters are correctly verified before processing. Organizations should prioritize this update as part of their regular patch management cycle.

For official patch details, see the Google Chrome Update Announcement.

Workarounds

• Restrict browsing to trusted websites until patching is complete to reduce exposure to crafted HTML pages
• Consider using browser isolation technologies to contain potential renderer compromises
• Implement network-level controls to monitor and restrict WebSocket connections from untrusted sources
• Enable Chrome's Site Isolation feature if not already enabled to limit renderer compromise impact

# Configuration example - Verify Chrome version on Linux/macOS
google-chrome --version
# Expected output should be 147.0.7727.55 or higher

# Force Chrome update check on enterprise systems
# Windows Group Policy or enterprise management tools recommended for deployment