CVE-2024-39424: Adobe Acrobat Use After Free Vulnerability

CVE-2024-39424 Overview

CVE-2024-39424 is a Use After Free vulnerability [CWE-416] affecting Adobe Acrobat and Acrobat Reader. The flaw exists in versions 20.005.30636, 24.002.20965, 24.002.20964, 24.001.30123, and earlier on Windows and macOS. Successful exploitation results in arbitrary code execution in the context of the current user. Exploitation requires user interaction, since a victim must open a crafted malicious file. Adobe published fixes in security bulletin APSB24-57.

Critical Impact

Attackers can execute arbitrary code with the privileges of the user who opens a malicious PDF, enabling initial access, credential theft, and lateral movement from a workstation.

Affected Products

• Adobe Acrobat and Acrobat DC (Classic and Continuous tracks)
• Adobe Acrobat Reader and Acrobat Reader DC (Classic and Continuous tracks)
• Microsoft Windows and Apple macOS installations of the above products

Discovery Timeline

• 2024-08-14 - CVE-2024-39424 published to the National Vulnerability Database
• 2026-06-17 - Last updated in the NVD database

Technical Details for CVE-2024-39424

Vulnerability Analysis

CVE-2024-39424 is a Use After Free defect in Adobe Acrobat and Acrobat Reader's document parsing paths. A Use After Free occurs when a program continues to reference memory after that memory has been released back to the allocator. When Acrobat processes a specially crafted PDF, the affected object is freed but a dangling pointer remains reachable through subsequent operations.

An attacker who controls the reallocation of the freed region can place attacker-influenced data where the stale pointer expects a valid object. Dereferencing that pointer then transfers control or corrupts adjacent state, enabling arbitrary code execution in the process context. Because Acrobat runs as the invoking user, execution inherits that user's privileges and access to local files, network shares, and stored credentials. The EPSS score of roughly 2.96% places this issue in the 86th percentile of observed exploitation likelihood.

Root Cause

The root cause is improper object lifetime management in Acrobat's PDF parsing or scripting engine. An internal object is deallocated while another code path still holds a reference to it. Subsequent access to that reference reads or writes memory that has been reassigned to attacker-controlled data.

Attack Vector

The vector is local and requires user interaction. An attacker delivers a malicious PDF through email, chat, a web download, or a shared drive. When the victim opens the file in a vulnerable build of Acrobat or Reader, the crafted objects trigger the Use After Free and hand execution to the attacker.

No verified public proof-of-concept code is available for CVE-2024-39424. Refer to the Adobe Acrobat Security Advisory APSB24-57 for vendor technical details.

Detection Methods for CVE-2024-39424

Indicators of Compromise

• Acrobat or Reader processes (Acrobat.exe, AcroRd32.exe) spawning shells, scripting hosts, or LOLBins such as cmd.exe, powershell.exe, wscript.exe, or mshta.exe
• Unexpected child processes or DLL loads from user-writable paths shortly after a PDF is opened
• Acrobat crashes or Windows Error Reporting entries referencing access violations in PDF rendering modules
• Outbound network connections from Acrobat processes to previously unseen domains or IP addresses

Detection Strategies

• Alert on any process creation where the parent is Acrobat.exe or AcroRd32.exe and the child is a scripting or shell interpreter.
• Hunt for PDF files delivered via email or web that contain embedded JavaScript, unusual object streams, or malformed cross-reference tables.
• Correlate Acrobat crash events with subsequent process creation, file write, or network activity on the same host.

Monitoring Recommendations

• Ingest endpoint process, file, and network telemetry into a central data lake and retain at least 90 days for retrospective hunts.
• Monitor installed Acrobat and Reader versions across the fleet and flag hosts running builds at or below 24.002.20965, 24.001.30123, or 20.005.30636.
• Track email gateway and web proxy logs for PDF attachments from untrusted senders and correlate with endpoint execution events.

How to Mitigate CVE-2024-39424

Immediate Actions Required

• Apply the updates listed in Adobe security bulletin APSB24-57 to all Acrobat and Reader installations on Windows and macOS.
• Inventory endpoints and prioritize patching for users who regularly handle external PDF documents.
• Restrict execution of Acrobat plug-ins and JavaScript in PDFs where business processes allow it.
• Educate users to avoid opening unsolicited PDF attachments and to report suspicious files.

Patch Information

Adobe released fixed versions in Adobe Security Bulletin APSB24-57. Upgrade Acrobat DC and Reader DC (Continuous track) and Acrobat 2020 (Classic track) to the versions published in that advisory. Enable the built-in automatic update mechanism to reduce time-to-patch on managed endpoints.

Workarounds

• Enable Protected View and Protected Mode (sandbox) in Acrobat and Reader to constrain the impact of exploitation.
• Disable JavaScript execution in Acrobat via Preferences or Group Policy where feasible.
• Block or quarantine inbound PDF attachments from external senders at the email gateway until patching is complete.

# Windows registry example: disable Acrobat JavaScript and enforce Protected View
reg add "HKCU\Software\Adobe\Acrobat Reader\DC\JSPrefs" /v bEnableJS /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Adobe\Acrobat Reader\DC\TrustManager" /v iProtectedView /t REG_DWORD /d 2 /f