CVE-2022-3075

What is Chromium Mojo?

Mojo is the inter-process communication (IPC) framework used by Google Chromium and all Chromium-based browsers (including Google Chrome, Microsoft Edge, Brave, and Opera) to enable message passing between the browser's multiple processes. Chromium uses a multi-process architecture for security: web content renders in an isolated renderer process, while privileged operations (file access, GPU, network) are handled by separate processes. Mojo handles all communication between these processes. Vulnerabilities in Mojo's message handling are critical because they sit at the sandbox boundary — a flaw that allows a compromised renderer to send malformed IPC messages to privileged processes can enable a full sandbox escape, converting a web-content exploitation from a sandboxed renderer compromise to full OS-level code execution.

Overview

CVE-2022-3075 is a critical insufficient data validation vulnerability (CWE-20, CVSS 9.6) in Google Chromium's Mojo IPC framework. An attacker who has already compromised the renderer process (e.g., via a separate renderer exploitation) can send crafted Mojo messages that bypass validation and trigger a sandbox escape, achieving code execution outside the renderer sandbox. Google confirmed active in-the-wild exploitation when releasing the emergency fix on September 2, 2022 — the sixth Chrome zero-day of 2022. The vulnerability affects all Chromium-based browsers.

Affected Versions

Technical Details

The vulnerability (CWE-20: Improper Input Validation) exists in Mojo's IPC message deserialization or message handler validation layer. When the renderer process sends a Mojo IPC message to a privileged browser process, the receiving process validates the message structure and parameters. In CVE-2022-3075, a specific message type or field fails to validate its value range, type, or pointer bounds correctly.

An attacker who has achieved code execution in the renderer process (through a separate renderer vulnerability) can craft a malformed Mojo message that passes the insufficient validation checks. This causes the privileged receiving process to operate on attacker-controlled data in an unsafe manner — triggering memory corruption or a type confusion that can be exploited for code execution in the privileged process context, outside the renderer sandbox.

The practical attack chain is:

1. Attacker gains renderer code execution via a separate browser vulnerability (e.g., a JavaScript engine bug or heap exploit)
2. The renderer process sends a crafted Mojo IPC message that exploits CVE-2022-3075
3. The privileged browser process processes the malformed message and is exploited
4. The attacker achieves full OS-level code execution outside the Chromium sandbox

The "scope changed" CVSS metric reflects that the vulnerability crosses the security sandbox boundary.

Discovery

Reported to Google by an anonymous researcher. Google's advisory acknowledged active exploitation in the wild before the patch was released — indicating the vulnerability was being used by threat actors (likely as part of a browser exploit chain) prior to Google's disclosure on September 2, 2022.

Exploitation Context

Browser sandbox escape vulnerabilities like CVE-2022-3075 are among the most valuable in the exploit market, typically used in high-value targeted attacks:

• Nation-state espionage: Government-sponsored actors use browser exploit chains to compromise journalist, activist, government, and defense contractor endpoints through phishing links or watering hole attacks
• Zero-day brokers: Vendors like Zerodium pay high premiums for Chromium sandbox escapes; confirmed in-the-wild use before Google's patch suggests the exploit was in active use before it was discovered by Google
• APT initial access: Browser zero-day chains (renderer exploit + sandbox escape) allow one-click compromise of a target who visits a malicious page — a preferred technique for APT groups targeting high-value individuals

2022 saw a record number of Chrome zero-days (seven total), with CVE-2022-3075 being the sixth. The frequency suggests organized threat actors specifically investing in Chromium vulnerability research.

Remediation

1. Update Chrome immediately: Install Chrome 105.0.5195.102 or later. Chrome auto-updates — verify version in Help > About Google Chrome.
2. Update all Chromium-based browsers: Microsoft Edge, Brave, Opera, and other Chromium-based browsers contain the same Mojo codebase and require their own patched updates.
3. Enable automatic updates: Ensure browser automatic update is enabled (default) to receive future emergency patches without manual action.
4. Enterprise patch deployment: Use Intune, SCCM, or MDM to push emergency browser updates to all managed endpoints outside normal patch cycle schedules for zero-days with confirmed in-the-wild exploitation.
5. Monitor for exploitation indicators: Browser sandbox escapes are typically paired with additional payloads. Monitor endpoints for unexpected process creation originating from browser processes after suspicious browser activity.