CVE-2023-21579: Adobe Acrobat DC RCE Vulnerability

CVE-2023-21579 Overview

CVE-2023-21579 is an Integer Overflow or Wraparound vulnerability affecting Adobe Acrobat and Acrobat Reader products across both Windows and macOS platforms. This vulnerability allows attackers to achieve arbitrary code execution in the context of the current user when a victim opens a specially crafted malicious PDF file.

The vulnerability stems from improper handling of integer arithmetic operations, which can lead to memory corruption conditions. An attacker who successfully exploits this vulnerability could execute arbitrary code with the same privileges as the logged-in user, potentially leading to complete system compromise if the user has elevated privileges.

Critical Impact

Successful exploitation enables arbitrary code execution in the context of the current user, potentially allowing attackers to install malware, steal sensitive data, or gain persistent access to compromised systems through malicious PDF documents.

Affected Products

• Adobe Acrobat DC (Continuous) version 22.003.20282 and earlier
• Adobe Acrobat Reader DC (Continuous) version 22.003.20281 and earlier
• Adobe Acrobat (Classic) version 20.005.30418 and earlier
• Adobe Acrobat Reader (Classic) version 20.005.30418 and earlier
• Affected on Microsoft Windows and Apple macOS platforms

Discovery Timeline

• 2023-01-18 - CVE-2023-21579 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-21579

Vulnerability Analysis

This vulnerability is classified as CWE-190 (Integer Overflow or Wraparound), a memory corruption issue that occurs when an arithmetic operation attempts to create a numeric value that is outside the range that can be represented with a given number of digits. In the context of Adobe Acrobat Reader, this integer overflow condition can corrupt memory structures used by the PDF rendering engine.

When processing certain PDF elements, the application performs arithmetic calculations on user-controlled input without adequate bounds checking. If the result of these calculations exceeds the maximum value that can be stored in the integer variable, the value wraps around to a small or negative number. This unexpected value is then used in subsequent memory allocation or buffer operations, leading to heap or stack corruption that can be leveraged for code execution.

The attack requires local access, meaning the attacker must deliver the malicious PDF file to the victim through phishing emails, malicious websites, or other social engineering techniques. User interaction is required as the victim must open the malicious file, which triggers the vulnerable code path during PDF parsing and rendering.

Root Cause

The root cause lies in insufficient validation of integer values during PDF processing operations. When the application calculates buffer sizes or array indices based on values read from a PDF file, it fails to verify that the resulting computed values remain within safe bounds. This allows an attacker to craft PDF content with specific values that cause integer overflow during arithmetic operations, resulting in undersized buffer allocations or out-of-bounds memory access.

Attack Vector

The attack vector is local, requiring user interaction to open a malicious PDF document. The typical attack scenario involves:

1. An attacker crafts a malicious PDF file containing specially constructed elements designed to trigger the integer overflow condition
2. The attacker delivers the malicious PDF to the victim via email attachment, web download, or file share
3. When the victim opens the PDF with a vulnerable version of Adobe Acrobat or Reader, the integer overflow occurs during file parsing
4. The corrupted memory state is exploited to redirect execution flow to attacker-controlled code
5. Arbitrary code executes with the privileges of the current user

The vulnerability requires no special privileges (PR:N) but does require user interaction (UI:R) to open the malicious document.

Detection Methods for CVE-2023-21579

Indicators of Compromise

• Unusual PDF files with abnormally large or malformed embedded objects
• Adobe Acrobat or Reader processes exhibiting unexpected memory consumption patterns
• Crash reports from AcroRd32.exe or Acrobat.exe indicating memory corruption
• Suspicious child processes spawned by Adobe Acrobat or Reader applications
• PDF files containing unusually large integer values in stream objects or font descriptors

Detection Strategies

• Monitor for abnormal process behavior from Adobe Acrobat or Reader, including unexpected child process creation or network connections
• Implement endpoint detection rules to identify PDF files with malformed or suspicious structures before they reach users
• Deploy application whitelisting to prevent unauthorized code execution from Adobe process context
• Enable detailed crash dump collection for Adobe products to identify potential exploitation attempts
• Utilize sandbox analysis for PDF attachments received via email to detect exploitation attempts

Monitoring Recommendations

• Enable Windows Event Logging for process creation events (Event ID 4688) with command line auditing to detect suspicious child processes from Adobe applications
• Configure SentinelOne Singularity Platform to monitor for behavioral anomalies in Adobe Acrobat processes
• Implement email gateway scanning for malicious PDF attachments before delivery to end users
• Monitor for unsigned DLL loading or reflective code injection within Adobe Acrobat process space
• Track file access patterns for Adobe Reader to identify attempts to access sensitive system files

How to Mitigate CVE-2023-21579

Immediate Actions Required

• Update Adobe Acrobat DC to version 22.003.20310 or later immediately
• Update Adobe Acrobat Reader DC to version 22.003.20310 or later immediately
• Update Adobe Acrobat (Classic 2020) to version 20.005.30436 or later
• Enable Protected Mode and Protected View in Adobe Acrobat/Reader settings
• Disable JavaScript in Adobe Acrobat/Reader if not required for business operations

Patch Information

Adobe has released security updates addressing this vulnerability in Adobe Security Bulletin APSB23-01. Organizations should apply the following updates:

• Adobe Acrobat DC (Continuous): Update to version 22.003.20310 or later
• Adobe Acrobat Reader DC (Continuous): Update to version 22.003.20310 or later
• Adobe Acrobat 2020 (Classic): Update to version 20.005.30436 or later
• Adobe Acrobat Reader 2020 (Classic): Update to version 20.005.30436 or later

The patches are available through Adobe's automatic update mechanism or can be downloaded directly from Adobe's website. Enterprise administrators can deploy updates through Adobe Admin Console or software distribution tools.

Workarounds

• Enable Protected View for all files in Adobe Acrobat/Reader preferences under Edit > Preferences > Security (Enhanced)
• Configure Adobe Reader to open PDF files in a sandboxed environment
• Implement Group Policy settings to restrict JavaScript execution in PDF documents
• Use alternative PDF readers with isolated sandboxing capabilities for untrusted documents
• Deploy email attachment filtering to quarantine PDF files from unknown or untrusted sources for analysis

# Windows Registry configuration to enable Protected View
reg add "HKCU\Software\Adobe\Acrobat Reader\DC\TrustManager" /v bEnableProtectedModeAtStartup /t REG_DWORD /d 1 /f
reg add "HKCU\Software\Adobe\Acrobat Reader\DC\TrustManager" /v iProtectedView /t REG_DWORD /d 2 /f