CVE-2024-9256 Overview
CVE-2024-9256 is an out-of-bounds read vulnerability [CWE-125] in Foxit PDF Reader and Foxit PDF Editor. The flaw resides in the handling of AcroForms, where the application fails to properly validate user-supplied data. Attackers can craft a malicious PDF file that, when opened by a user, reads memory past the end of an allocated buffer. The disclosed data can be chained with other vulnerabilities to achieve arbitrary code execution in the context of the current process. The issue was reported through Trend Micro's Zero Day Initiative as ZDI-CAN-25267.
Critical Impact
An attacker can disclose sensitive process memory from Foxit PDF Reader or Editor via a malicious PDF, enabling follow-on exploitation for arbitrary code execution.
Affected Products
- Foxit PDF Reader (Windows)
- Foxit PDF Editor (Windows)
- Multiple versions prior to the vendor security bulletin fix
Discovery Timeline
- 2024-11-22 - CVE-2024-9256 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-9256
Vulnerability Analysis
The vulnerability affects the AcroForms processing component within Foxit PDF Reader and Foxit PDF Editor. AcroForms is Adobe's PDF form technology that supports embedded JavaScript, dynamic fields, and complex data structures. Foxit's parser processes attacker-controlled form data without adequate bounds checking. This allows a read past the end of an allocated buffer, exposing adjacent process memory to the malicious document.
Information disclosed through this out-of-bounds read can include heap metadata, object pointers, and other runtime data. Attackers commonly chain such reads with memory corruption bugs to bypass Address Space Layout Randomization (ASLR) and achieve reliable arbitrary code execution.
Root Cause
The root cause is missing validation of user-supplied fields within AcroForm objects during parsing. The affected code path calculates a read size or offset from attacker-controlled input without confirming the value stays within the bounds of the source buffer. When the calculated read extends past the allocation, adjacent memory contents are returned to caller logic that can expose them through form callbacks or JavaScript hooks.
Attack Vector
Exploitation requires user interaction. The victim must open a malicious PDF in Foxit PDF Reader or Foxit PDF Editor, or visit a web page that delivers the document to the vulnerable application. The attack executes with the privileges of the current user process. Successful exploitation leaks memory contents that an attacker can pair with other flaws to execute arbitrary code.
No verified public proof-of-concept code is available. For a technical breakdown of the affected AcroForm code path, refer to the Zero Day Initiative Advisory ZDI-24-1309.
Detection Methods for CVE-2024-9256
Indicators of Compromise
- Unexpected crashes or hangs of FoxitPDFReader.exe or FoxitPDFEditor.exe shortly after opening a PDF from email or the web
- PDF documents containing malformed or unusually large AcroForm field definitions delivered by phishing campaigns
- Foxit application processes spawning unexpected child processes such as cmd.exe, powershell.exe, or scripting hosts
Detection Strategies
- Inspect inbound PDFs at the mail gateway and web proxy for oversized or malformed /AcroForm and /XFA dictionaries
- Alert on Foxit reader or editor processes performing outbound network connections or writing executables to disk
- Monitor for module load events in Foxit processes that indicate scripting engines invoking form callbacks with anomalous parameters
Monitoring Recommendations
- Enable Windows Event Tracing (ETW) and endpoint telemetry on process creation, image load, and file open events for Foxit binaries
- Correlate PDF open events with subsequent memory access violations reported in Windows Error Reporting
- Track software inventory to ensure all Foxit installations are patched against CVE-2024-9256
How to Mitigate CVE-2024-9256
Immediate Actions Required
- Update Foxit PDF Reader and Foxit PDF Editor to the versions listed in the vendor security bulletin
- Restrict opening of untrusted PDF documents until endpoints are patched
- Verify enterprise deployment tooling has pushed the update to all managed workstations
Patch Information
Foxit has released updated builds addressing this out-of-bounds read. Consult the Foxit Security Bulletins for the exact fixed versions for Reader and Editor on Windows. Apply the update through Foxit's built-in updater or enterprise software distribution.
Workarounds
- Disable JavaScript in Foxit under Preferences to reduce AcroForm callback exposure
- Configure Safe Reading Mode to block execution of embedded actions in untrusted documents
- Use group policy or application allowlisting to prevent Foxit from launching child processes
- Route PDF attachments through a sandboxed viewer or detonation service before delivery to end users
# Example: enforce Safe Reading Mode via registry on Windows endpoints
reg add "HKCU\Software\Foxit Software\Foxit PDF Reader\Preferences\Trust Manager" /v bSafeMode /t REG_DWORD /d 1 /f
reg add "HKCU\Software\Foxit Software\Foxit PDF Reader\Preferences\JavaScript" /v bEnableJS /t REG_DWORD /d 0 /f
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
