CVE-2023-26405: Adobe Acrobat Reader RCE Vulnerability

CVE-2023-26405 Overview

CVE-2023-26405 is an Improper Input Validation vulnerability affecting Adobe Acrobat Reader that could result in arbitrary code execution in the context of the current user. This vulnerability allows attackers to craft malicious PDF files that, when opened by a victim, can execute arbitrary code on the target system. The attack requires user interaction—specifically, the victim must open a malicious file for exploitation to occur.

Critical Impact

Successful exploitation enables attackers to execute arbitrary code with the privileges of the current user, potentially leading to complete system compromise, data theft, or lateral movement within an organization.

Affected Products

• Adobe Acrobat Reader versions 23.001.20093 and earlier (Continuous track)
• Adobe Acrobat Reader versions 20.005.30441 and earlier (Classic track)
• Adobe Acrobat DC (Continuous track)
• Adobe Acrobat (Classic track)
• Affected on both Microsoft Windows and Apple macOS platforms

Discovery Timeline

• 2023-04-12 - CVE-2023-26405 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-26405

Vulnerability Analysis

This vulnerability stems from improper input validation (CWE-20) within Adobe Acrobat Reader's file parsing functionality. When processing specially crafted PDF documents, the application fails to properly validate certain input parameters before using them in critical operations. This lack of validation creates an exploitable condition that attackers can leverage to execute arbitrary code.

The vulnerability affects local file processing operations, meaning an attacker must deliver a malicious PDF file to the victim through phishing emails, compromised websites, or other social engineering techniques. Once the victim opens the malicious document, the exploit triggers without any additional interaction required.

Root Cause

The root cause of CVE-2023-26405 is insufficient input validation within Adobe Acrobat Reader's document processing engine. The application does not adequately verify the integrity and bounds of certain input data within PDF files before processing them. This improper validation allows malformed or malicious data to be processed in unexpected ways, ultimately leading to arbitrary code execution.

The CWE-20 (Improper Input Validation) classification indicates that the vulnerability exists because the software does not validate or incorrectly validates input that can affect the control flow or data flow of a program.

Attack Vector

The attack vector for this vulnerability requires local access through user interaction. An attacker would typically craft a malicious PDF document designed to exploit the input validation flaw and distribute it to potential victims through various channels:

1. Email phishing campaigns - Sending the malicious PDF as an attachment or linking to it
2. Compromised websites - Hosting the malicious PDF for download or embedding it in web pages
3. File sharing services - Distributing through cloud storage or collaboration platforms
4. Social engineering - Convincing users to open the document through various pretexts

When the victim opens the malicious PDF file with a vulnerable version of Adobe Acrobat Reader, the exploit executes code in the context of the current user, potentially gaining full control over the affected system.

Detection Methods for CVE-2023-26405

Indicators of Compromise

• Suspicious PDF files with unusual embedded objects or JavaScript code
• Adobe Acrobat Reader processes spawning unexpected child processes
• Anomalous network connections originating from AcroRd32.exe or Acrobat.exe
• Unexpected file system modifications following PDF document access

Detection Strategies

• Monitor for Adobe Acrobat Reader processes executing unusual system commands or spawning shell processes
• Implement endpoint detection rules to identify malicious PDF file characteristics and embedded exploit payloads
• Deploy network-based detection for known malicious PDF signatures and exploit patterns
• Review Adobe Acrobat Reader crash dumps and error logs for exploitation attempts

Monitoring Recommendations

• Enable enhanced logging for Adobe Acrobat Reader application events
• Implement behavioral analysis on endpoints to detect post-exploitation activities
• Monitor for suspicious file downloads with PDF extensions from untrusted sources
• Configure SIEM rules to correlate PDF document access with subsequent suspicious process behavior

How to Mitigate CVE-2023-26405

Immediate Actions Required

• Update Adobe Acrobat Reader and Adobe Acrobat to the latest patched versions immediately
• Enable automatic updates for Adobe products to ensure timely security patches
• Educate users about the risks of opening PDF documents from untrusted sources
• Consider implementing application whitelisting to prevent unauthorized code execution

Patch Information

Adobe has released security updates addressing this vulnerability as documented in Adobe Security Advisory APSB23-24. Organizations should apply these patches to all affected systems immediately.

For Continuous track users, update to Adobe Acrobat Reader DC version newer than 23.001.20093. For Classic track users, update to a version newer than 20.005.30441. The patches are available for both Windows and macOS platforms.

Workarounds

• Configure Adobe Acrobat Reader Protected View to open all files in Protected Mode by default
• Disable JavaScript execution in Adobe Acrobat Reader through Preferences > JavaScript settings
• Implement email gateway filtering to scan PDF attachments for known malicious patterns
• Consider using alternative PDF readers with sandboxing capabilities until patches can be deployed