CVE-2021-21190
📋 TL;DR
This vulnerability in Google Chrome's PDFium component allows attackers to read uninitialized memory from the browser process by tricking users into opening a malicious PDF file. This can leak sensitive information like passwords, cookies, or other data from memory. All Chrome users on versions before 89.0.4389.72 are affected.
💻 Affected Systems
- Google Chrome
- Chromium-based browsers
📦 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
Attackers could extract authentication tokens, passwords, or other sensitive data from browser memory, leading to account compromise or data theft.
Likely Case
Attackers could obtain fragments of memory containing user data or system information, potentially enabling further attacks.
If Mitigated
With proper controls, the impact is limited to information disclosure without direct system compromise.
🎯 Exploit Status
Exploitation requires user interaction to open a malicious PDF file.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 89.0.4389.72
Vendor Advisory: https://chromereleases.googleblog.com/2021/03/stable-channel-update-for-desktop.html
Restart Required: Yes
Instructions:
1. Open Chrome settings. 2. Click 'About Chrome'. 3. Chrome will automatically check for and install updates. 4. Restart Chrome when prompted.
🔧 Temporary Workarounds
Disable PDF preview in Chrome
allConfigure Chrome to download PDFs instead of opening them in the browser
chrome://settings/content/pdfDocuments
Toggle 'Download PDF files instead of automatically opening them in Chrome' to ON
🧯 If You Can't Patch
- Use alternative PDF viewers or open PDFs in sandboxed environments
- Implement network filtering to block PDF downloads from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check Chrome version in settings. If version is below 89.0.4389.72, the system is vulnerable.Check Version:
chrome://version/Verify Fix Applied:
Confirm Chrome version is 89.0.4389.72 or higher in settings.📡 Detection & Monitoring
Log Indicators:
- Multiple PDF file downloads from suspicious sources
- Chrome crash reports related to PDF rendering
Network Indicators:
- Unusual PDF file downloads from external sources
- PDF files with abnormal structure or size
SIEM Query:
source="chrome" AND (event="pdf_download" OR event="crash") AND file_extension="pdf"🔗 References
- https://chromereleases.googleblog.com/2021/03/stable-channel-update-for-desktop.html
- https://crbug.com/1166091
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BBT54RKAE5XLMWSHLVUKJ7T2XHHYMXLH/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FE5SIKEVYTMDCC5OSXGOM2KRPYLHYMQX/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LCIDZ77XUDMB2EBPPWCQXPEIJERDNSNT/
- https://www.debian.org/security/2021/dsa-4886
- https://chromereleases.googleblog.com/2021/03/stable-channel-update-for-desktop.html
- https://crbug.com/1166091
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BBT54RKAE5XLMWSHLVUKJ7T2XHHYMXLH/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FE5SIKEVYTMDCC5OSXGOM2KRPYLHYMQX/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LCIDZ77XUDMB2EBPPWCQXPEIJERDNSNT/
- https://www.debian.org/security/2021/dsa-4886
