CVE-2022-24954: Foxit PDF Reader Buffer Overflow Flaw

CVE-2022-24954 Overview

CVE-2022-24954 is a stack-based buffer overflow vulnerability affecting Foxit PDF Reader and Foxit PDF Editor versions prior to 11.2.1 on Windows systems. The vulnerability exists in the XFA (XML Forms Architecture) processing component, specifically triggered when handling malformed subform colSpan="-2" and draw colSpan="1" substrings within PDF documents.

This memory corruption vulnerability allows remote attackers to potentially execute arbitrary code on victim systems by crafting malicious PDF documents. The attack requires no user authentication and can be delivered via network vectors such as email attachments or malicious downloads.

Critical Impact

Remote code execution via malicious PDF documents, potentially leading to complete system compromise without authentication requirements.

Affected Products

• Foxit PDF Reader versions before 11.2.1 on Windows
• Foxit PDF Editor versions before 11.2.1 on Windows
• Microsoft Windows (as the underlying operating system platform)

Discovery Timeline

• 2022-02-11 - CVE-2022-24954 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-24954

Vulnerability Analysis

The vulnerability is classified as CWE-787 (Out-of-bounds Write), manifesting as a stack-based buffer overflow within Foxit's XFA processing engine. XFA is an XML-based specification used for creating interactive PDF forms, and Foxit's implementation contains improper boundary checking when parsing certain XFA elements.

When processing PDF documents containing XFA forms with specific colSpan attribute values, particularly negative integers like -2, the application fails to properly validate input before copying data to a fixed-size stack buffer. This allows attackers to overflow the buffer and potentially overwrite critical memory structures including the return address on the stack.

The vulnerability can be exploited without any user interaction beyond opening a malicious PDF file, making it particularly dangerous for drive-by attacks or phishing campaigns. Successful exploitation could allow an attacker to gain code execution with the privileges of the user running Foxit PDF Reader or Editor.

Root Cause

The root cause of this vulnerability lies in insufficient input validation within Foxit's XFA parsing routines. Specifically, the colSpan attribute parser does not properly handle negative integer values or edge-case combinations of subform and draw element parameters.

When the parser encounters a subform colSpan="-2" combined with draw colSpan="1" elements, it triggers a calculation error in buffer size allocation, leading to a classic stack-based buffer overflow condition. The lack of proper bounds checking allows attacker-controlled data to be written beyond the intended buffer boundaries.

Attack Vector

The attack is network-based and requires an attacker to deliver a specially crafted PDF document to the victim. Attack scenarios include:

1. Email phishing: Attacker sends a malicious PDF as an email attachment
2. Malicious downloads: Victim downloads a weaponized PDF from a compromised or attacker-controlled website
3. Document sharing platforms: Malicious PDFs uploaded to file sharing services

The vulnerability is triggered when the victim opens the malicious PDF document in an unpatched version of Foxit PDF Reader or Editor. The malformed XFA elements cause the buffer overflow, potentially allowing the attacker to redirect execution flow and run arbitrary code.

The attack complexity is low, requiring no special privileges or user interaction beyond opening the document. The exploitation mechanism leverages the XFA form processing functionality that is automatically parsed when opening compatible PDF files.

Detection Methods for CVE-2022-24954

Indicators of Compromise

• Unexpected crashes or abnormal termination of Foxit PDF Reader or Editor processes
• Suspicious PDF files containing malformed XFA elements with negative colSpan values
• Unusual child processes spawned from Foxit applications
• Memory access violation errors logged in Windows Event Viewer associated with Foxit processes

Detection Strategies

• Deploy endpoint detection and response (EDR) solutions to monitor for exploitation attempts and abnormal PDF processing behavior
• Implement file scanning rules to detect PDF documents containing suspicious XFA elements with malformed colSpan attributes
• Monitor for unusual process behavior from FoxitPDFReader.exe and FoxitPDFEditor.exe including unexpected memory allocation patterns
• Enable crash dump collection to capture exploitation attempts for forensic analysis

Monitoring Recommendations

• Establish baseline behavior for Foxit applications and alert on deviations such as unexpected network connections or child process creation
• Implement logging for PDF file access events across the organization to track potential malicious document distribution
• Monitor for repeated application crashes that may indicate exploitation attempts
• Deploy network-level inspection for PDF files in transit to identify potentially malicious documents before they reach endpoints

How to Mitigate CVE-2022-24954

Immediate Actions Required

• Update Foxit PDF Reader to version 11.2.1 or later immediately
• Update Foxit PDF Editor to version 11.2.1 or later immediately
• Audit systems to identify all instances of vulnerable Foxit software versions
• Consider temporarily disabling or restricting PDF document access from untrusted sources until patches are applied

Patch Information

Foxit has released security updates that address this vulnerability. Users should update to Foxit PDF Reader version 11.2.1 or later and Foxit PDF Editor version 11.2.1 or later. The official security bulletins and patch downloads are available through the Foxit Security Bulletins page.

Organizations should prioritize deployment of these patches given the critical severity rating and the potential for remote code execution without authentication.

Workarounds

• Implement strict policies to block PDF attachments from untrusted sources at email gateways
• Configure Foxit applications in "Safe Reading Mode" if available, which may limit XFA form execution
• Use alternative PDF readers for documents from untrusted sources until patching is complete
• Deploy application whitelisting to prevent unauthorized code execution even if exploitation occurs

# Configuration example - Verify Foxit PDF Reader version on Windows
# Check installed version via PowerShell
Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*" | Where-Object {$_.DisplayName -like "*Foxit*"} | Select-Object DisplayName, DisplayVersion

# Alternative: Check version via command line
wmic product where "name like '%%Foxit%%'" get name, version