CVE-2021-30599: Google Chrome V8 RCE Vulnerability

CVE-2021-30599 Overview

CVE-2021-30599 is a type confusion vulnerability in the V8 JavaScript engine used by Google Chrome prior to version 92.0.4515.159. A remote attacker can execute arbitrary code inside the Chrome sandbox by serving a crafted HTML page to a victim. The flaw is categorized under CWE-843 (Access of Resource Using Incompatible Type). Exploitation requires user interaction in the form of visiting a malicious or compromised web page. Google addressed the issue in the August 2021 stable channel update, and Fedora distributed corresponding package updates for Fedora 33, 34, and 35.

Critical Impact

A successful exploit allows arbitrary code execution within the Chrome renderer sandbox, providing an attacker a foothold for sandbox escape chains.

Affected Products

• Google Chrome prior to 92.0.4515.159
• Fedora 33, 34, and 35 (Chromium package builds)
• Any Chromium-based application bundling the vulnerable V8 engine

Discovery Timeline

• 2021-08-26 - CVE-2021-30599 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-30599

Vulnerability Analysis

The vulnerability resides in V8, the open-source JavaScript and WebAssembly engine that powers Chrome. Type confusion occurs when code allocates or accesses a resource using one type but later interprets it as an incompatible type. In V8, this typically manifests during just-in-time (JIT) compilation or when optimization passes make incorrect assumptions about object shapes (hidden classes/maps).

When V8 misinterprets the underlying type, attacker-controlled data can be treated as a pointer, function, or object reference. This primitive enables out-of-bounds reads and writes within the renderer's address space. From there, an attacker can pivot to arbitrary code execution within the sandboxed renderer process. Exploitation is constrained by Chrome's site isolation and sandbox boundaries, but the renderer compromise commonly serves as the first stage in a chain that pairs with a separate sandbox escape vulnerability.

Root Cause

The root cause is improper type checking in V8 [CWE-843]. The engine fails to validate that an object's actual type matches the type assumed by optimized code paths. Detailed technical specifics are restricted in the Chrome Bug Report #1234770, which remains access-controlled to limit weaponization.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker hosts a crafted HTML page containing JavaScript that triggers the type confusion in V8. Delivery typically occurs through phishing links, malicious advertisements, watering-hole attacks, or compromised legitimate sites. No authentication or prior access is needed.

No public proof-of-concept code is available for this issue. Refer to the Google Chrome Stable Update advisory for vendor details.

Detection Methods for CVE-2021-30599

Indicators of Compromise

• Chrome or Chromium browser processes spawning unexpected child processes such as command shells, scripting interpreters, or rundll32.exe.
• Renderer process crashes accompanied by JavaScript heap corruption signatures in Chrome crash reports.
• Outbound network connections from a Chrome renderer to uncategorized or newly registered domains immediately after page load.

Detection Strategies

• Inventory Chrome installations and flag any endpoint running a version earlier than 92.0.4515.159 for remediation tracking.
• Inspect browser telemetry for anomalous JavaScript execution patterns, including heavy use of typed arrays, ArrayBuffer manipulation, and repeated map transitions on the same object.
• Correlate web proxy logs with endpoint process telemetry to identify URLs preceding renderer crashes or suspicious child process creation.

Monitoring Recommendations

• Enforce centralized browser version reporting through enterprise management policies and alert on out-of-date installations.
• Monitor for Chrome renderer processes performing file system writes outside the standard profile and cache directories.
• Forward Chrome crash dump metadata and EDR telemetry to a central analytics pipeline for retrospective hunting on V8-related signatures.

How to Mitigate CVE-2021-30599

Immediate Actions Required

• Update Google Chrome to version 92.0.4515.159 or later on all managed endpoints.
• Apply the corresponding Fedora package updates for Fedora 33, 34, and 35 referenced in the Fedora package announcements.
• Restart browsers after patch deployment to ensure the vulnerable V8 engine is no longer loaded in memory.

Patch Information

Google released the fix in the Chrome stable channel update documented at Google Chrome Stable Update. Fedora distributed corresponding builds via the Fedora Package Announcement (5LVY4WIWTVVYKQMROJJS365TZBKEARCF), Fedora Package Announcement (IPJPUSAWIJMQFBQQQYXAICLI4EKFQOH6), and Fedora Package Announcement (QW4R2K5HVJ4R6XDZYOJCCFPIN2XHNS3L).

Workarounds

• Restrict browsing to trusted sites using web filtering or DNS-layer protection while patching is in progress.
• Disable JavaScript for untrusted origins via enterprise policy where business workflows allow.
• Deploy site isolation and strict sandbox policies through Chrome enterprise configuration to limit the impact of renderer compromise.

# Verify Chrome version on Linux endpoints
google-chrome --version

# Update Chromium on Fedora
sudo dnf upgrade --refresh chromium

# Force Chrome update check on Windows via policy
reg add "HKLM\Software\Policies\Google\Update" /v UpdateDefault /t REG_DWORD /d 1 /f