CVE-2024-6778: Google Chrome DevTools XSS Vulnerability

CVE-2024-6778 Overview

CVE-2024-6778 is a race condition vulnerability in the DevTools component of Google Chrome versions prior to 126.0.6478.182. An attacker who convinces a user to install a malicious extension can exploit the race to inject scripts or HTML into privileged pages. Successful exploitation breaks the boundary between extension context and Chrome's internal pages, enabling escalation beyond standard extension permissions. Chromium rated the security severity as High, and Google addressed the flaw in the stable channel desktop update. The vulnerability is tracked under [CWE-362] (concurrent execution using shared resource) and [CWE-366] (race condition within a thread).

Critical Impact
Attackers leveraging a malicious extension can inject code into privileged Chrome pages, breaking the extension sandbox boundary and gaining elevated access within the browser.

Affected Products

Google Chrome desktop versions prior to 126.0.6478.182
All platforms running affected Chromium-based builds (Windows, macOS, Linux)
Chromium-derived browsers that had not merged the upstream fix at release time

Discovery Timeline

2024-07-16 - CVE-2024-6778 published to NVD
2024-12-26 - Last updated in NVD database

Technical Details for CVE-2024-6778

Vulnerability Analysis

The flaw is a race condition in Chrome's DevTools subsystem. DevTools interacts with privileged internal pages such as chrome:// URLs that hold elevated browser capabilities. The race window allows a malicious extension to interleave operations and place attacker-controlled scripts or HTML into a page context that should be off-limits to extensions. Once injected, code executes with the privileges of the target page rather than the extension's normal sandbox. This converts an extension-level foothold into broader browser-level control, including access to APIs and data that extensions cannot normally reach. The issue is classified under [CWE-362] and [CWE-366], reflecting unsynchronized access to shared state during DevTools operations.

Root Cause

The root cause is improper synchronization between DevTools operations and page navigation or document lifecycle events. When a crafted extension triggers DevTools actions in a specific order, the browser fails to enforce the security boundary that separates extension scripts from privileged page contexts. The Chromium issue tracker entry 341136300 documents the underlying fix.

Attack Vector

Exploitation requires user interaction. The victim must install a malicious Chrome extension authored by the attacker. The attack vector is network-reachable because extensions are typically distributed via web channels, but attack complexity is high due to the timing required to win the race. Once installed, the extension triggers the DevTools race to inject payloads into privileged pages and escalate within the browser.

No verified public proof-of-concept code is available. See the Chromium Issue Tracker Entry and the Google Chrome Desktop Update for technical details from the vendor.

Detection Methods for CVE-2024-6778

Indicators of Compromise

Installation of unsigned or sideloaded Chrome extensions from outside the Chrome Web Store
Extensions requesting debugger API permissions or interacting with DevTools protocol endpoints
Unexpected child processes or script execution originating from Chrome renderer processes tied to chrome:// pages
Chrome versions below 126.0.6478.182 present on managed endpoints

Detection Strategies

Inventory installed browser extensions across the fleet and flag those not on an approved allowlist
Monitor Chrome update telemetry to identify endpoints lagging behind the patched build
Hunt for extension manifests that declare the debugger permission combined with broad host permissions
Correlate process telemetry that shows Chrome spawning scripting interpreters or accessing sensitive local files following extension install events

Monitoring Recommendations

Enable enterprise browser management to enforce the ExtensionInstallAllowlist and ExtensionInstallBlocklist policies
Stream endpoint and browser telemetry into a centralized data lake for retrospective hunting on extension activity
Alert on Chrome process anomalies such as unusual command-line flags, DevTools protocol usage, or remote debugging port exposure

How to Mitigate CVE-2024-6778

Immediate Actions Required

Update Chrome to version 126.0.6478.182 or later on all managed endpoints
Audit installed extensions and remove any that are unapproved, sideloaded, or request debugger permissions without justification
Enforce automatic Chrome updates through enterprise policy to close the patch window quickly
Restrict extension installation to a vetted allowlist managed through Chrome Enterprise policies

Patch Information

Google fixed the issue in the Chrome Stable channel release 126.0.6478.182 for desktop. Details are published in the Google Chrome Desktop Update advisory. Administrators should verify the running version via chrome://version and confirm the patched build is deployed across Windows, macOS, and Linux endpoints.

Workarounds

Block installation of all third-party extensions until patched Chrome builds are deployed
Disable the Chrome --remote-debugging-port flag and restrict DevTools usage on production endpoints
Apply the ExtensionInstallBlocklist policy with a wildcard * and selectively allowlist trusted extension IDs

bash

# Chrome Enterprise policy example to restrict extensions (Linux managed policy JSON)
# /etc/opt/chrome/policies/managed/extension_policy.json
{
  "ExtensionInstallBlocklist": ["*"],
  "ExtensionInstallAllowlist": [
    "<approved-extension-id-1>",
    "<approved-extension-id-2>"
  ],
  "DeveloperToolsAvailability": 2
}