Google Chrome and FreeType Heap Buffer Overflow Vulnerability (CVE-2020-15999) Technical Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTGoogle Chrome versions prior to 86.0.4240.111 and FreeType library versions prior to 2.10.4
Remote attackers can trigger heap corruption and potentially execute arbitrary code via a specially crafted HTML page or font file
Immediately upgrade Google Chrome to version 86.0.4240.111 or later, and update the FreeType library to version 2.10.4 or higher
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Update Google Chrome to the latest stable channel. For Linux servers and containerized environments, execute the following commands to upgrade Chrome and the FreeType library:
# For Debian/Ubuntu-based systems
sudo apt-get update && sudo apt-get --only-upgrade install -y google-chrome-stable libfreetype6
# For RedHat/CentOS-based systems
sudo yum update -y google-chrome-stable freetype2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict outbound access to untrusted external websites and block the download of untrusted web fonts (.ttf, .otf, .woff) at the network perimeter or reverse proxy level.
# Example Nginx configuration to block external web font requests
location ~* \.(ttf|otf|woff|woff2)$ {
deny all;
access_log off;
log_not_found off;
}3. Log Audit & IoC Verification Commands
Use the following script to verify the installed versions of Google Chrome and FreeType to identify potential exposure.
# Check the installed FreeType library version on Linux
ldconfig -p | grep freetype
# Verify Google Chrome version and check vulnerability status
CHROME_VER=$(google-chrome --version | awk '{print $3}')
SAFE_VER='86.0.4240.111'
if [ '$(printf '%s\
' "$SAFE_VER" "$CHROME_VER" | sort -V | head -n1)' = "$SAFE_VER" ]; then
echo '[SAFE] Chrome is running a patched version.'
else
echo '[WARNING] Vulnerable Chrome version detected: '$CHROME_VER
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2020-15999) is a critical heap buffer overflow (CWE-787) in the FreeType font rendering library, which is utilized by Google Chrome for processing embedded fonts. The root cause lies within the Load_SBit_Png function, which processes PNG images embedded inside TrueType/OpenType fonts. Due to insufficient validation of the image dimensions (width and height) specified in the font metadata, the library allocates an inadequate heap buffer size, leading to an out-of-bounds write when the actual PNG bitmap data is copied into the buffer.
2. Exploitation Mechanics & Attack Scenario
An attacker can exploit this vulnerability by crafting a malicious font file containing a specifically structured PNG image. The primary attack vector involves hosting this malicious font on a website and enticing users to visit the page. When Google Chrome attempts to render the web font using the vulnerable FreeType library, the parsing logic triggers a heap buffer overflow. This corrupts adjacent heap memory, which can lead to a renderer process crash or, when combined with a sandbox escape vulnerability, full remote code execution (RCE) on the victim's machine.
3. Infrastructure & Business Impact
As a zero-day vulnerability actively exploited in the wild, CVE-2020-15999 poses a severe threat to enterprise environments. It is listed in the CISA KEV catalog and carries a high EPSS score of 0.6389. Successful exploitation allows attackers to compromise employee workstations silently via drive-by downloads, serving as an initial entry point for lateral movement, ransomware deployment, and sensitive data exfiltration.
Official Vendor Advisories & References
Heap buffer overflow in Freetype in Google Chrome prior to 86.0.4240.111 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.
Frequently Asked SecOps Questions (CVE-2020-15999)
FAQQ1. How critical is CVE-2020-15999 and is it actively exploited in the wild?
CVE-2020-15999 is rated CVSS 9.6 (CRITICAL) with a 30-day EPSS exploitation probability of 63.9%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2020-15999?
Primary impacted vendors include google, freetype across chrome, freetype. Scope summary: Google Chrome prior to 86.0.4240.111 (all desktop platforms) and FreeType library prior to 2.10.4
Q3. What temporary mitigations or workarounds exist for CVE-2020-15999 before patching?
[Mitigation] Immediately upgrade Google Chrome to version 86.0.4240.111 or later, and update the FreeType library to version 2.10.4 or higher Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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