CVE-2021-31459 in Foxit
Summary
by MITRE • 05/08/2021
This vulnerability allows remote attackers to execute arbitrary code on affected installations of Foxit Reader 10.1.1.37576. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The specific flaw exists within the handling of XFA Forms. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-13162.
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Analysis
by VulDB Data Team • 05/04/2026
CVE-2021-31459 represents a critical remote code execution vulnerability affecting Foxit Reader version 10.1.1.37576 and potentially other versions within the same product line. This vulnerability resides in the XFA Forms processing component of the PDF reader application, making it particularly dangerous as PDF documents are commonly shared across networks and organizations. The flaw stems from inadequate input validation within the object handling mechanisms, specifically when processing XFA (XML Forms Architecture) forms embedded within PDF files. According to CWE-476, this vulnerability maps directly to a null pointer dereference scenario where the application fails to validate object existence before attempting operations on those objects. The vulnerability operates under the ATT&CK framework category of T1203, which encompasses exploitation for execution through malicious file delivery or web-based attacks.
The technical exploitation of this vulnerability requires a user to interact with malicious content, either by visiting a compromised website hosting a malicious PDF or by opening a specially crafted PDF file. This user interaction requirement makes the attack surface somewhat limited compared to fully automated exploits, but it remains highly concerning given the widespread use of PDF readers in enterprise environments. When a vulnerable Foxit Reader instance processes an XFA form containing malicious code, the application's failure to validate object references leads to a situation where arbitrary code can be executed within the context of the current process. This execution context typically corresponds to the privileges of the user running the application, potentially allowing attackers to access sensitive data, install malware, or escalate privileges depending on the user's permissions.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with a potential foothold for more sophisticated attacks within target networks. Organizations using Foxit Reader in their document processing workflows face significant risk, particularly in environments where users frequently open PDF files from untrusted sources. The vulnerability's exploitation requires minimal technical skill from attackers, making it attractive for automated attack campaigns. Security professionals should consider this vulnerability as part of broader threat modeling exercises, especially in environments where PDF processing is common and where users may not be adequately trained about the risks of opening untrusted documents. The vulnerability's classification as a remote code execution flaw places it in the same category as other high-severity vulnerabilities that have historically led to widespread compromise of endpoint systems.
Organizations should prioritize immediate patching of affected Foxit Reader installations, as no reliable workarounds exist for this vulnerability. The patching process should include comprehensive testing in controlled environments before deployment to production systems. Network security teams should implement monitoring for suspicious PDF-related activities and consider blocking PDF files from untrusted sources through email filters and web proxies. Additionally, user education programs should emphasize the dangers of opening PDF files from unknown sources and the importance of verifying document authenticity before processing. Security teams should also consider implementing sandboxing techniques for PDF processing to contain potential exploitation attempts, though this approach may impact user experience and system performance. The vulnerability's presence in a widely-used commercial PDF reader underscores the importance of maintaining current security patches and conducting regular vulnerability assessments of third-party software components within organizational networks.