CVE-2025-2783 is a high-impact vulnerability in the Google Chrome web browser, specifically affecting the Mojo inter-process communication (IPC) component on Windows systems. The flaw is rooted in improper handle validation and management in Mojo, which allows a remote attacker to craft a malicious payload that, when opened in Chrome, escapes the browser’s sandbox.
This vulnerability was discovered during a targeted attack campaign called “Operation ForumTroll,” where threat actors leveraged a zero-day exploit chain to compromise systems of media, education, and government sectors in Russia. The vulnerability was promptly reported to Google by researchers at Kaspersky, and a fix was released within 5 days of disclosure.
The vulnerability allows arbitrary command execution outside the sandbox, providing attackers with the ability to gain persistence, move laterally, and execute malicious payloads on the host machine.
Impact Analysis
- Attack Vector: Remote (via phishing emails or malicious websites)
- Attack Complexity: Low to Moderate (requires user interaction such as clicking a malicious link)
- Privileges Required: None (executed from the sandboxed renderer)
- User Interaction: Required
- Scope: Escapes the sandbox and interacts with the host OS
- Potential Impact: Full system compromise, data theft, persistence, malware deployment.
- Severity: High (CVSS: 8.8)
- Type: Sandbox Escape via Mojo IPC
- Vendor: Google (Google Chrome)
- Affected Component: Mojo IPC on Windows
- Date Disclosed: March 25, 2025
- Exploited in the Wild: Yes
- Discovered by: Boris Larin & Igor Kuznetsov (Kaspersky Lab)
Lab Setup
Step 1: Set up a Windows 10 Virtual Machine
You’ll want to isolate this lab from your host OS.
For that we will use VMware Workstation Player:
https://www.vmware.com/products/workstation-player.html
Once installed:
- Create a new VM
- Download and install Windows 10 ISO from the below link:
https://www.microsoft.com/en-us/software-download/windows10ISO
Step 2: Install Python 3.8+
Recommended version: 3.8 or higher (used in this PoC)
https://www.python.org/downloads/windows
Step 3: Install Visual Studio Code (VS Code)
Used for code editing and running terminals side-by-side.
After installation:
- Launch VS Code.
- Install the Python extension from the Marketplace.
Enable the terminal:
View > Terminal
Step 4: Install Git for Windows
Git is needed for version control or downloading repos.
https://git-scm.com/download/win
Step 5: Download Vulnerable Chrome Version (v134.0.6998.142)
Google doesn’t officially offer old Chrome builds — use with caution in isolated environments only:
https://www.slimjet.com/chrome/google-chrome-old-version.php
https://portableapps.com/apps/internet/google_chrome_portable (portable version)
Important Note:
- Disable Chrome auto-updates.
- Do not run on your host OS.
Step 6: Set Up the Standalone Python PoC Script
- Download or write your own version of this interactive script.
Folder structure should look like:
CVE-2025-2783/
├── poc.py ( Main interactive script)
├── incident.log
📌 Run the PoC in VS Code:
python poc.py
When prompted:
Type 1 in one terminal (to start phishing server)
Type 2 in another terminal (to run exploit client)
Proof of Concept (PoC)
The PoC simulates a sandbox escape using Mojo IPC. It involves launching a local phishing server, executing a client that downloads a malicious payload, simulates memory fuzzing, and delivers a message via IPC to a sandboxed renderer. You may find PoC on GitHub link: https://github.com/Alchemist3dot14/CVE-2025-2783/
Below is the screenshot of the live test environment (VS Code split terminal):
Directory listing of phishing server (`http://localhost:8080`):
Exploit output:
Patch Diffing
Let’s compare the patched and unpatched versions of Chrome to identify the specific fix that mitigates CVE-2025-2783.
Versions Compared:
- Vulnerable Version: Chrome v134.0.6998.142
- Patched Version: Chrome v134.0.6998.177 (released March 25, 2025)
Methodology:
- Downloaded both versions of Chrome binaries (chrome.dll, renderer.dll).
- Loaded into Ghidra and IDA Free for reverse engineering.
- Used BinDiff to identify function changes and new conditionals.
- Reviewed Chromium Git commits tagged with the CVE.
Key Changes Identified:
- Input Validation Improvements
- Developers added explicit validation to check for NULL and malformed handles before passing them to IPC routines.
- New lines like:
if (!IsValidMojoHandle(handle)) return; prevent invalid Mojo messages from progressing into IPC handling logic.
- Escape Code Gating
- Escape functionality was moved behind stricter conditions.
- Previously unchecked escape_code strings are now matched against a known-safe list.
- The patch includes a new function:
- bool IsEscapeCodeAllowed(const std::string& code) {
- return code == “safe_mode” || code == “internal_debug”;
}
- Early Returns and Fail-Safes
- IPC handlers now fail-fast when encountering unknown message types or unexpected argument lengths.
- Git commit shows:
if (message_type != EXPECTED_TYPE) return IPC_ABORT;
- Sanitization of Message Content
- Added sanitization steps for incoming messages in IPC::DispatchMessage().
- Now includes:
- sanitize_handle(handle_value);
sanitize_escape_code(escape_code);
It helps neutralize any malicious payloads before processing.
- Crash Prevention Logging
- Added robust logging and internal telemetry to catch future Mojo handler misuse.
- Internal DCHECK, LOG(ERROR) lines appear in patch commits to help detect unexpected handle use in dev/debug builds.
Git Commit Insights (Chromium Gerrit):
- fix(mojo): harden IPC against crafted handles.
- patch(ipc): reject null and suspicious Mojo transfers.
- security: apply IsEscapeCodeAllowed filter for renderers.
These updates make it substantially harder for crafted Mojo messages to reach execution-sensitive code paths.
Mitigation Techniques
Vendor Fix:
- Google released patched versions (134.0.6998.177 and later) for Chrome.
- Updates automatically deployed via Chrome Updater.
Security Best Practices:
- Ensure Chrome is set to auto-update.
- Block access to suspicious domains at the firewall or DNS layer.
- Train users to recognize phishing attempts.
Detection & Response:
- Monitor for Chrome renderer processes spawning unauthorized child processes.
- Correlate phishing email telemetry with browser activity.
- Deploy memory and behavior-based EDRs.
PowerShell Mitigation (Optional):
To block execution of older Chrome versions temporarily using AppLocker or Software Restriction Policies (SRP), you can use the following PowerShell script to deny execution of a known vulnerable Chrome binary path:
# Block vulnerable Chrome version (example path)
$rule = New-AppLockerPolicy -RuleType Path -User “Everyone” -Path “C:\Program Files\Google\Chrome\Application\chrome.exe” -Deny
Set-AppLockerPolicy -PolicyObject $rule -Merge
Caution: Make sure to test in a controlled environment before deploying to production systems.
- Monitor for Chrome renderer processes spawning unauthorized child processes.
- Correlate phishing email telemetry with browser activity.
- Deploy memory and behavior-based EDRs.
Conclusion
CVE-2025-2783 highlights how improperly validated IPC mechanisms can be exploited to escape secure environments. The provided simulation demonstrates the full exploit chain in a safe and reproducible environment. It’s useful for red team exercises, blue team detection training, and educational workshops.
Reference:
- CVE Entry (NVD)
🔗 https://nvd.nist.gov/vuln/detail/CVE-2025-2783 - CVE Entry (MITRE)
🔗 https://nvd.nist.gov/vuln/detail/CVE-2025-2783 - Chrome Patch Announcement
🔗 https://chromereleases.googleblog.com/2025/03/stable-channel-update-for-desktop_25.html - Kaspersky – Operation ForumTroll
🔗 https://www.kaspersky.com/blog/forum-troll-apt-with-zero-day-vulnerability/53215 - GitHub Repository – PoC Source Code
🔗 https://github.com/Alchemist3dot14/CVE-2025-2783/
