CVE-2021-21150
📋 TL;DR
This is a use-after-free vulnerability in Google Chrome's Downloads component on Windows that allows a remote attacker who has already compromised the renderer process to potentially escape the browser sandbox. Attackers could execute arbitrary code with higher privileges by tricking users into visiting a malicious HTML page. This affects Chrome users on Windows systems prior to version 88.0.4324.182.
💻 Affected Systems
- Google Chrome
📦 What is this software?
Chrome by Google
Google Chrome is the world's most popular web browser, used by over 3 billion users globally across Windows, macOS, Linux, Android, and iOS platforms. As a Chromium-based browser developed by Google, Chrome dominates the browser market with approximately 65% market share, making it a critical compon...
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⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining SYSTEM-level privileges, enabling installation of persistent malware, data theft, and lateral movement across the network.
Likely Case
Attacker escapes Chrome sandbox to execute code with user-level privileges, potentially stealing credentials, installing keyloggers, or accessing local files.
If Mitigated
With proper patching, the vulnerability is eliminated; with Chrome's sandbox intact, impact is limited to the renderer process only.
🎯 Exploit Status
Exploitation requires chaining with another vulnerability to first compromise the renderer process, then triggering the use-after-free to escape the sandbox.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 88.0.4324.182
Vendor Advisory: https://chromereleases.googleblog.com/2021/02/stable-channel-update-for-desktop_16.html
Restart Required: Yes
Instructions:
1. Open Chrome. 2. Click the three-dot menu → Help → About Google Chrome. 3. Chrome will automatically check for and install updates. 4. Click 'Relaunch' to restart Chrome with the patched version.
🔧 Temporary Workarounds
Disable Chrome Downloads
windowsPrevents exploitation by disabling the vulnerable Downloads component via group policy or registry settings.
Windows Registry: HKEY_LOCAL_MACHINE\Software\Policies\Google\Chrome\DownloadRestrictions = 4
Use Alternative Browser
allTemporarily switch to a non-vulnerable browser until Chrome can be patched.
🧯 If You Can't Patch
- Restrict user access to untrusted websites via web filtering or proxy policies.
- Implement application whitelisting to prevent execution of unauthorized binaries that might result from exploitation.
🔍 How to Verify
Check if Vulnerable:
Check Chrome version: if below 88.0.4324.182 on Windows, the system is vulnerable.Check Version:
chrome://version/Verify Fix Applied:
Confirm Chrome version is 88.0.4324.182 or higher after update.📡 Detection & Monitoring
Log Indicators:
- Chrome crash reports with memory corruption signatures
- Unexpected child process creation from chrome.exe
Network Indicators:
- Unusual outbound connections from Chrome processes to external IPs
SIEM Query:
Process Creation where ParentImage contains 'chrome.exe' and CommandLine contains unusual parameters🔗 References
- https://chromereleases.googleblog.com/2021/02/stable-channel-update-for-desktop_16.html
- https://crbug.com/1172192
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BI6ZIJQYP5DFMYVX4J5OGOU2NQLEZ3SB/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FE5SIKEVYTMDCC5OSXGOM2KRPYLHYMQX/
- https://security.gentoo.org/glsa/202104-08
- https://chromereleases.googleblog.com/2021/02/stable-channel-update-for-desktop_16.html
- https://crbug.com/1172192
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BI6ZIJQYP5DFMYVX4J5OGOU2NQLEZ3SB/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FE5SIKEVYTMDCC5OSXGOM2KRPYLHYMQX/
- https://security.gentoo.org/glsa/202104-08
