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 versions prior to 86.0.4240.75. A remote attacker can trigger heap corruption by convincing a user to visit a crafted HTML page, potentially leading to arbitrary code execution within the browser renderer process. The flaw is classified under CWE-416: Use After Free.

The vulnerability affects Google Chrome and downstream consumers of the WebRTC library, including Apple Safari, iPadOS, iOS, macOS, tvOS, and watchOS. Linux distributions including Debian, Fedora, openSUSE, and Gentoo also shipped patched packages.

Critical Impact
Remote attackers can exploit heap corruption through a crafted HTML page to achieve code execution in the browser context after a single user interaction.

Affected Products

Google Chrome prior to 86.0.4240.75
Apple Safari, iPadOS, iOS, macOS, tvOS, and watchOS (shared WebRTC code)
Debian 10, Fedora 31/32/33, openSUSE Backports SLE 15 SP2

Discovery Timeline

2020-11-03 - CVE-2020-15969 published to the National Vulnerability Database
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-15969

Vulnerability Analysis

The vulnerability resides in the Web Real-Time Communication (WebRTC) subsystem used by Chromium-based browsers and other downstream products. A use-after-free condition occurs when WebRTC code references a heap object after that object has already been freed. An attacker who controls the timing and contents of subsequent allocations can place attacker-controlled data into the freed memory region.

When the dangling pointer is later dereferenced, the browser operates on attacker-influenced data. This primitive enables heap corruption that can be escalated to arbitrary code execution inside the renderer process. WebRTC parses media and signaling data attacker-supplied JavaScript can invoke through standard Web APIs, making the attack surface reachable from any web page.

Root Cause

The root cause is improper object lifetime management within WebRTC. A reference to a freed object persists beyond its valid scope, violating memory safety guarantees. Public Chromium bug 1124659 tracks the issue but remains restricted, so the precise object and call path are not publicly disclosed.

Attack Vector

Exploitation requires user interaction. A victim must load a malicious or compromised web page that issues crafted WebRTC API calls to trigger the freed-object reuse. No authentication or elevated privileges are required, and the attack succeeds entirely over the network. The Exploit Prediction Scoring System (EPSS) places this CVE in the 87th percentile, indicating elevated likelihood of exploitation relative to other published CVEs.

No public proof-of-concept exploit is listed in Exploit-DB, and the vulnerability is not present in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2020-15969

Indicators of Compromise

Renderer process crashes correlated with visits to untrusted pages that initiate RTCPeerConnection or getUserMedia calls.
Unexpected child processes spawned by chrome.exe, Safari, or other WebRTC-consuming applications following browser activity.
Outbound connections to unfamiliar STUN/TURN endpoints from browser processes on hosts running outdated Chrome builds.

Detection Strategies

Inventory installed browser versions and flag any Chrome build older than 86.0.4240.75 or Apple platforms missing the updates referenced in HT212003, HT212005, HT212007, HT212009, and HT212011.
Monitor endpoint telemetry for renderer process crashes with access-violation signatures originating from WebRTC modules.
Correlate web proxy logs with endpoint browser version data to identify exposed hosts visiting media-rich or untrusted content.

Monitoring Recommendations

Forward browser crash dumps and process telemetry to a centralized analytics platform for behavioral baselining.
Alert on post-exploitation behavior such as renderer processes writing to disk outside of sandbox-permitted paths or initiating non-browser outbound traffic.
Track patch compliance for Chrome and Apple WebKit-based products through vulnerability management scans.

How to Mitigate CVE-2020-15969

Immediate Actions Required

Update Google Chrome to 86.0.4240.75 or later on every endpoint.
Apply Apple platform updates documented in HT212003, HT212005, HT212007, HT212009, and HT212011 for Safari, iOS, iPadOS, macOS, tvOS, and watchOS.
Update Linux packages using vendor advisories: Debian DSA-4824, Gentoo GLSA 202101-30, and the Fedora package announcements.
Restart browsers after patching to ensure the vulnerable code is unloaded from memory.

Patch Information

Google addressed the vulnerability in the Chrome stable channel update announced in the Chrome Releases blog. The fix is tracked in Chromium bug 1124659. Apple integrated the corresponding WebRTC fix into its platform updates released in late 2020.

Workarounds

Disable WebRTC functionality through enterprise policy where business workflows do not require peer-to-peer media. Chrome supports the WebRtcAllowLegacyTLSProtocols and related policies, but full disablement requires extensions or build flags.
Restrict browsing to trusted sites using web filtering or isolation technologies until patches are deployed.
Enforce site isolation and the renderer sandbox to limit the impact of successful renderer compromise.

bash

# Verify the installed Chrome version on Linux endpoints
google-chrome --version

# Example Debian patch deployment
sudo apt-get update && sudo apt-get install --only-upgrade google-chrome-stable

# Confirm the patched build (must be >= 86.0.4240.75)
google-chrome --version | awk '{print $3}'