CVE-2020-3763: Adobe Acrobat DC Privilege Escalation Flaw

CVE-2020-3763 Overview

CVE-2020-3763 is a privilege escalation vulnerability affecting Adobe Acrobat and Reader products across multiple versions and tracks. This vulnerability allows an attacker to exploit improper privilege handling within the application, potentially leading to arbitrary file system write operations. The ability to write arbitrary files to the file system can be leveraged for further exploitation, including code execution, persistence mechanisms, or data manipulation.

Critical Impact

Successful exploitation of this vulnerability enables arbitrary file system write operations, potentially allowing attackers to overwrite critical system files, implant malicious payloads, or escalate privileges to gain full system control.

Affected Products

• Adobe Acrobat DC (Continuous and Classic tracks) versions 2019.021.20061 and earlier
• Adobe Acrobat Reader DC (Continuous and Classic tracks) versions 2019.021.20061 and earlier
• Adobe Acrobat 2017 (Classic 2017) versions 2017.011.30156 and earlier
• Adobe Acrobat Reader 2017 (Classic 2017) versions 2017.011.30156 and earlier
• Adobe Acrobat 2015 (Classic 2015) versions 2015.006.30508 and earlier
• Adobe Acrobat Reader 2015 (Classic 2015) versions 2015.006.30508 and earlier

Discovery Timeline

• February 13, 2020 - CVE-2020-3763 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-3763

Vulnerability Analysis

This privilege escalation vulnerability exists within Adobe Acrobat and Reader's handling of certain operations that can be exploited to perform arbitrary file system writes. The vulnerability affects both Windows and macOS platforms, indicating a cross-platform issue in the core application logic rather than platform-specific code.

The network attack vector suggests that the vulnerability can be triggered through maliciously crafted PDF documents delivered via email, web downloads, or other network-based delivery mechanisms. Once a user opens a malicious PDF, the vulnerability can be exploited without requiring additional user interaction or elevated privileges, making it particularly dangerous in enterprise environments where PDF documents are commonly exchanged.

Root Cause

The root cause of CVE-2020-3763 lies in improper privilege handling within Adobe Acrobat and Reader. The application fails to adequately validate or restrict certain operations that interact with the file system, allowing attackers to bypass intended security boundaries. This insufficient access control enables write operations to file system locations that should be protected, effectively escalating the privileges available to the attacker beyond what the application should permit.

Attack Vector

The attack vector for this vulnerability is network-based, requiring an attacker to craft a malicious PDF document that exploits the privilege escalation flaw. The attack scenario typically involves:

1. An attacker creates a specially crafted PDF document containing embedded elements designed to trigger the vulnerability
2. The malicious PDF is delivered to victims via email attachments, malicious websites, or file-sharing services
3. When a victim opens the PDF with a vulnerable version of Adobe Acrobat or Reader, the exploit executes
4. The vulnerability is triggered, allowing the attacker to perform arbitrary file system writes
5. The attacker can use this capability to drop malicious payloads, modify system configurations, or establish persistence

The exploitation does not require any authentication or additional user interaction beyond opening the malicious document, making social engineering attacks highly effective.

Detection Methods for CVE-2020-3763

Indicators of Compromise

• Unexpected file creation or modification in system directories by Adobe Acrobat or Reader processes
• Suspicious child processes spawned from AcroRd32.exe, Acrobat.exe, or their macOS equivalents
• Unusual file system write operations originating from PDF reader applications to protected locations
• Presence of recently modified PDF files with unusual embedded content or JavaScript

Detection Strategies

• Monitor process behavior for Adobe Acrobat and Reader applications attempting to write files outside typical user document directories
• Implement endpoint detection rules to identify privilege escalation attempts from PDF reader processes
• Deploy file integrity monitoring on critical system directories to detect unauthorized modifications
• Use application control policies to baseline normal Adobe Reader behavior and alert on anomalies

Monitoring Recommendations

• Enable verbose logging for Adobe Acrobat and Reader applications where possible
• Configure SIEM rules to correlate PDF document opens with subsequent suspicious file system activity
• Monitor for creation of executable files or script files following PDF document access
• Review Windows Event Logs or macOS unified logs for anomalous file system operations tied to Adobe processes

How to Mitigate CVE-2020-3763

Immediate Actions Required

• Update all Adobe Acrobat and Reader installations to the latest available versions immediately
• Enable Protected View in Adobe Reader to open documents from untrusted sources in a restricted mode
• Disable JavaScript execution in Adobe Reader if not required for business operations
• Implement email attachment scanning to detect and quarantine potentially malicious PDF files

Patch Information

Adobe has released security updates addressing CVE-2020-3763 in security bulletin APSB20-05. Organizations should update to the following minimum versions or later:

• Adobe Acrobat DC and Reader DC Continuous: 2020.006.20034
• Adobe Acrobat 2017 and Reader 2017 Classic 2017: 2017.011.30158
• Adobe Acrobat 2015 and Reader 2015 Classic 2015: 2015.006.30510

Organizations using enterprise deployment tools should prioritize pushing these updates to all endpoints with Adobe Acrobat or Reader installed.

Workarounds

• Enable Protected View for all files by navigating to Edit > Preferences > Security (Enhanced) and selecting "Files from potentially unsafe locations"
• Disable JavaScript in Adobe Reader via Edit > Preferences > JavaScript > Uncheck "Enable Acrobat JavaScript"
• Consider using alternative PDF readers for viewing untrusted documents while patches are being deployed
• Implement application whitelisting to prevent unauthorized code execution even if the vulnerability is exploited

# Windows Registry: Enable Protected View for all files
reg add "HKCU\Software\Adobe\Acrobat Reader\DC\TrustManager" /v bEnableProtectedModeAppContainer /t REG_DWORD /d 1 /f

# Windows Registry: Disable JavaScript in Adobe Reader DC
reg add "HKCU\Software\Adobe\Acrobat Reader\DC\JSPrefs" /v bEnableJS /t REG_DWORD /d 0 /f