CVE-2020-9596: Adobe Acrobat DC Auth Bypass Vulnerability

CVE-2020-9596 Overview

CVE-2020-9596 is a security bypass vulnerability affecting Adobe Acrobat and Reader across multiple versions and tracks. This vulnerability allows attackers to circumvent security features implemented within the application, potentially enabling malicious actions that would otherwise be blocked by the software's built-in protections. The vulnerability requires local access and user interaction to exploit, typically through a specially crafted PDF document.

Critical Impact

Successful exploitation of this vulnerability could lead to a complete bypass of security features in Adobe Acrobat and Reader, potentially allowing attackers to execute malicious code or perform unauthorized actions with the privileges of the current user.

Affected Products

• Adobe Acrobat DC (Continuous and Classic tracks) versions 2020.006.20042 and earlier
• Adobe Acrobat Reader DC (Continuous and Classic tracks) versions 2020.006.20042 and earlier
• Adobe Acrobat 2017 (Classic 2017) versions 2017.011.30166 and earlier
• Adobe Acrobat Reader 2017 (Classic 2017) versions 2017.011.30166 and earlier
• Adobe Acrobat 2015 (Classic 2015) versions 2015.006.30518 and earlier
• Adobe Acrobat Reader 2015 (Classic 2015) versions 2015.006.30518 and earlier

Discovery Timeline

• June 25, 2020 - CVE-2020-9596 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-9596

Vulnerability Analysis

This security bypass vulnerability exists in Adobe Acrobat and Reader's security mechanisms. The flaw allows attackers to circumvent security controls that are designed to prevent malicious operations within PDF documents. When a user opens a maliciously crafted PDF file, the attacker can bypass security features that would normally restrict certain operations, potentially leading to compromise of confidentiality, integrity, and availability of the affected system.

The vulnerability requires local access, meaning the attacker must deliver the malicious PDF to the target system. User interaction is required as the victim must open the crafted document. Once exploited, the attacker can perform actions that should be blocked by the application's security model.

Root Cause

The vulnerability stems from improper implementation of security controls within Adobe Acrobat and Reader. The application fails to properly enforce security boundaries, allowing specially crafted content to bypass protective mechanisms. Adobe has classified this as a security bypass vulnerability, indicating that the fundamental issue lies in the enforcement logic of the application's security features rather than a memory corruption or input validation flaw.

Attack Vector

The attack vector for CVE-2020-9596 is local, requiring an attacker to either have direct access to the target system or to convince a user to open a malicious PDF document. The most common attack scenarios include:

1. Phishing campaigns: Delivering malicious PDF attachments via email
2. Drive-by downloads: Hosting malicious PDFs on compromised or attacker-controlled websites
3. Social engineering: Convincing users to download and open seemingly legitimate documents

The vulnerability affects both Windows and macOS platforms where Adobe Acrobat and Reader are installed. No public proof-of-concept exploits have been identified, and the vulnerability is not currently listed in CISA's Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2020-9596

Indicators of Compromise

• Unusual behavior from AcroRd32.exe or Acrobat.exe processes attempting to access restricted resources
• PDF documents with suspicious embedded content or JavaScript attempting to bypass security prompts
• Network connections initiated by Adobe Reader or Acrobat processes to unexpected destinations
• Unexpected child processes spawned by Adobe Acrobat or Reader applications

Detection Strategies

• Monitor for Adobe Acrobat and Reader processes exhibiting anomalous behavior or accessing sensitive system resources
• Implement endpoint detection rules to identify PDF files with potentially malicious embedded content
• Deploy network monitoring to detect suspicious outbound connections from Adobe processes
• Utilize application whitelisting to control what actions Adobe products can perform

Monitoring Recommendations

• Enable enhanced logging for Adobe Acrobat and Reader applications
• Configure SIEM rules to alert on suspicious PDF-related activity patterns
• Monitor file system activity for Adobe processes accessing or modifying unexpected locations
• Track JavaScript execution within PDF documents through Adobe's JavaScript debugging features

How to Mitigate CVE-2020-9596

Immediate Actions Required

• Update Adobe Acrobat DC (Continuous) to version 2020.009.20063 or later
• Update Adobe Acrobat Reader DC (Continuous) to version 2020.009.20063 or later
• Update Adobe Acrobat 2017 (Classic 2017) to version 2017.011.30171 or later
• Update Adobe Acrobat 2015 (Classic 2015) to version 2015.006.30523 or later
• Disable JavaScript in Adobe Reader/Acrobat if updates cannot be immediately applied

Patch Information

Adobe has released security updates to address this vulnerability as part of security bulletin APSB20-24. Organizations should apply the latest available updates for their respective Adobe Acrobat and Reader track (Continuous or Classic). The security advisory is available at the Adobe Acrobat Security Advisory page.

Workarounds

• Disable JavaScript execution in Adobe Acrobat and Reader through Edit > Preferences > JavaScript
• Enable Protected View for all files from untrusted sources
• Configure Adobe Reader/Acrobat to run in Protected Mode (sandbox)
• Implement network-level controls to scan PDF attachments before delivery to end users

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

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