CVE-2020-15969: Google Chrome Use-After-Free Vulnerability

CVE-2020-15969 Overview

CVE-2020-15969 is a use-after-free vulnerability in the WebRTC component of Google Chrome prior to version 86.0.4240.75. This memory corruption flaw allows a remote attacker to potentially exploit heap corruption via a crafted HTML page. The vulnerability affects multiple platforms and browsers that utilize the WebRTC implementation, including Google Chrome, Apple Safari, and various Apple operating systems.

Critical Impact

Remote attackers can achieve arbitrary code execution by exploiting heap corruption through maliciously crafted web content, potentially leading to full system compromise without requiring authentication.

Affected Products

• Google Chrome (versions prior to 86.0.4240.75)
• Apple Safari
• Apple iPadOS
• Apple iPhone OS
• Apple macOS
• Apple tvOS
• Apple watchOS
• Debian Linux 10.0
• Fedora 31, 32, 33
• openSUSE Backports SLE 15.0 SP2

Discovery Timeline

• November 3, 2020 - CVE-2020-15969 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-15969

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption issue where the application continues to use a pointer after the memory it references has been freed. In the context of WebRTC, this occurs when handling real-time communication streams in the browser. The freed memory can be reallocated for other purposes, and when the dangling pointer is dereferenced, it can lead to heap corruption, potentially allowing an attacker to control program execution flow.

The vulnerability requires user interaction—specifically, a victim must navigate to a malicious webpage containing the crafted HTML content. Once triggered, the attacker can potentially achieve remote code execution within the context of the browser process.

Root Cause

The root cause lies in improper memory management within Chrome's WebRTC implementation. When certain WebRTC objects are destroyed, their associated memory is freed, but references to these objects may persist elsewhere in the codebase. Subsequent operations that attempt to access these stale references result in use-after-free conditions, corrupting the heap and enabling exploitation.

Attack Vector

The attack is network-based and requires user interaction. An attacker would need to:

1. Craft a malicious HTML page containing JavaScript that triggers the vulnerable WebRTC code path
2. Lure a victim to visit the malicious page (via phishing, malvertising, or compromised websites)
3. Exploit the use-after-free condition to corrupt heap memory
4. Leverage the corruption to achieve arbitrary code execution

The exploitation involves manipulating heap memory layout to place controlled data in the freed memory region, which is then accessed through the dangling pointer. This technique is commonly used in browser exploitation to hijack control flow and execute attacker-supplied shellcode.

Detection Methods for CVE-2020-15969

Indicators of Compromise

• Unexpected browser crashes or instability when visiting web pages with WebRTC functionality
• Memory corruption indicators in browser crash dumps referencing WebRTC components
• Suspicious JavaScript execution patterns attempting to manipulate WebRTC objects rapidly
• Anomalous network connections following browser exploitation attempts

Detection Strategies

• Deploy browser-based exploit detection that monitors for heap spray patterns and memory corruption attempts
• Implement network-level inspection for known WebRTC exploitation payloads
• Monitor endpoint telemetry for browser process anomalies, including unexpected child processes or memory access violations
• Utilize SentinelOne's behavioral AI to detect post-exploitation activities following browser compromise

Monitoring Recommendations

• Enable detailed browser logging and crash reporting to capture exploitation attempts
• Monitor for unusual WebRTC connection patterns that may indicate reconnaissance or exploitation
• Track browser version deployments across the organization to identify vulnerable installations
• Implement web filtering to block access to known malicious domains serving exploit content

How to Mitigate CVE-2020-15969

Immediate Actions Required

• Update Google Chrome to version 86.0.4240.75 or later immediately
• Update Apple Safari and Apple operating systems (iOS, iPadOS, macOS, tvOS, watchOS) to the latest security releases
• Update affected Linux distributions (Debian, Fedora, openSUSE) with the latest Chromium/browser packages
• Consider disabling WebRTC functionality in browsers where it is not required until patches are applied

Patch Information

Google has released Chrome version 86.0.4240.75 which addresses this vulnerability. Detailed information is available in the Chrome Stable Channel Update. The original bug report can be found at Bug Report #1124659.

Apple has released security updates addressing this vulnerability across multiple products:

• Apple Security Update HT212003
• Apple Security Update HT212005
• Apple Security Update HT212007
• Apple Security Update HT212009
• Apple Security Update HT212011

Linux distribution patches are available via Debian Security DSA-4824, Gentoo GLSA 202101-30, and openSUSE Security Announcement.

Workarounds

• Disable WebRTC in browser settings if not needed for business operations (in Chrome, this requires extensions or enterprise policies)
• Implement strict Content Security Policy (CSP) headers to limit JavaScript execution on trusted origins only
• Use browser isolation technologies to contain potential exploitation attempts in sandboxed environments
• Deploy network segmentation to limit the impact of potential browser-based compromises

# Chrome Enterprise Policy to restrict WebRTC
# Add to Chrome policies JSON configuration
{
  "WebRtcAllowLegacyTLSProtocols": false,
  "WebRtcLocalIpsAllowedUrls": [],
  "WebRtcEventLogCollectionAllowed": false
}