CVE-2021-37975 Overview
CVE-2021-37975 is a Use After Free vulnerability in the V8 JavaScript engine used by Google Chrome prior to version 94.0.4606.71. This memory corruption flaw allows a remote attacker to potentially exploit heap corruption via a crafted HTML page, enabling arbitrary code execution in the context of the browser process.
Critical Impact
This vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. Attackers can achieve remote code execution by luring victims to malicious web pages, potentially compromising entire systems.
Affected Products
- Google Chrome (versions prior to 94.0.4606.71)
- Fedora 33, 34, and 35
- Debian Linux 10.0 and 11.0
Discovery Timeline
- 2021-10-08 - CVE-2021-37975 published to NVD
- 2025-10-24 - Last updated in NVD database
Technical Details for CVE-2021-37975
Vulnerability Analysis
This Use After Free (CWE-416) vulnerability exists in Google Chrome's V8 JavaScript engine, the high-performance open-source engine that powers both Chrome and Node.js. V8 compiles JavaScript to native machine code for execution, making it a critical security boundary between web content and the underlying system.
The vulnerability stems from a logic bug in V8's memory management during JavaScript execution. When certain JavaScript operations are performed in a specific sequence, V8 can prematurely free memory that is still referenced by other objects. Subsequent access to this freed memory results in a Use After Free condition, which can be exploited to corrupt heap metadata and gain arbitrary code execution.
Root Cause
The root cause is a logic flaw in V8's garbage collection and object lifecycle management. During specific code paths involving JavaScript object manipulation, the engine incorrectly marks memory as eligible for reclamation while active references still exist. This creates a dangling pointer scenario where legitimate code paths attempt to access memory that has already been returned to the allocator and potentially reallocated for other purposes.
Attack Vector
Exploitation occurs via the network attack vector, requiring user interaction to visit a malicious webpage. An attacker crafts a specially designed HTML page containing JavaScript code that triggers the vulnerable code path in V8. The attack sequence typically involves:
- Victim navigates to attacker-controlled or compromised webpage
- Malicious JavaScript triggers the logic bug in V8
- Memory is freed prematurely while still referenced
- Attacker manipulates heap layout to control freed memory contents
- Subsequent access to dangling pointer provides arbitrary read/write primitive
- Attacker achieves code execution within the Chrome renderer process
The vulnerability can be chained with sandbox escape techniques to achieve full system compromise. Technical analysis is available in the Packet Storm Logic Bug Analysis.
Detection Methods for CVE-2021-37975
Indicators of Compromise
- Unusual Chrome renderer process crashes or unexpected restarts
- JavaScript execution anomalies detected in browser telemetry
- Network connections to known malicious domains hosting exploit kits
- Memory corruption artifacts in Chrome crash dumps
Detection Strategies
- Monitor for Chrome version strings in network traffic and endpoint telemetry to identify unpatched installations
- Deploy endpoint detection rules for anomalous JavaScript execution patterns and heap spray indicators
- Implement network-based detection for known exploit kit landing pages and payloads
- Enable Chrome's built-in crash reporting and analyze crash dumps for Use After Free signatures
Monitoring Recommendations
- Establish baseline Chrome version deployment across the enterprise and alert on outdated versions
- Monitor for process behavior anomalies in Chrome renderer processes, including unusual memory allocation patterns
- Implement web proxy logging to track user navigation patterns and identify potential watering hole attacks
- Deploy SentinelOne's behavioral AI to detect post-exploitation activities following successful browser compromise
How to Mitigate CVE-2021-37975
Immediate Actions Required
- Update Google Chrome to version 94.0.4606.71 or later immediately
- Enable automatic Chrome updates across all managed endpoints
- Apply vendor security updates for Fedora and Debian Linux distributions
- Implement browser isolation for high-risk users to contain potential compromise
Patch Information
Google released a security patch addressing this vulnerability in the Chrome Stable Channel Update on September 30, 2021. Additional security advisories were issued by Debian (DSA-5046) and Fedora for their respective distributions. Organizations should verify Chrome installations are at version 94.0.4606.71 or later.
The vulnerability is tracked in Chromium Bug Report #1252918 and listed in the CISA Known Exploited Vulnerabilities Catalog.
Workarounds
- Disable JavaScript execution in Chrome via enterprise policies for sensitive operations until patching is complete
- Implement network-level blocking of known exploit kit domains and malicious payloads
- Deploy browser isolation solutions to execute untrusted web content in isolated environments
- Restrict users to approved website lists in high-security environments until systems are patched
# Chrome enterprise policy to force automatic updates
# Deploy via Group Policy or MDM
cat << 'EOF' > /etc/opt/chrome/policies/managed/update_policy.json
{
"AutoUpdateCheckPeriodMinutes": 60,
"RelaunchNotification": 2,
"RelaunchNotificationPeriod": 3600000
}
EOF
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
