CVE-2021-31457 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 Annotation objects. 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-13147.
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Analysis
by VulDB Data Team • 05/04/2026
The vulnerability identified as CVE-2021-31457 represents a critical remote code execution flaw within Foxit Reader version 10.1.1.37576, demonstrating a classic object validation error that has significant implications for document security. This vulnerability operates under the Common Weakness Enumeration framework as CWE-476, which specifically addresses NULL pointer dereferences and improper object validation. The flaw manifests in the annotation handling subsystem where the software fails to properly validate whether an object exists before attempting operations on it, creating a predictable execution path for malicious actors who can manipulate PDF documents to trigger this condition.
The exploitation mechanism requires user interaction through either visiting a malicious webpage or opening a crafted malicious file, making this vulnerability particularly dangerous in phishing scenarios or when users encounter compromised documents in legitimate business contexts. The vulnerability's impact extends beyond simple code execution as it operates within the context of the current process, meaning that successful exploitation could allow attackers to perform actions with the same privileges as the Foxit Reader application itself. This process context execution model aligns with ATT&CK technique T1059.007 for command and scripting interpreter, where adversaries leverage legitimate system tools to execute malicious code.
The technical root cause stems from inadequate input validation within the PDF annotation processing pipeline, where Foxit Reader does not properly verify object existence before dereferencing pointers to annotation objects. This creates a race condition or predictable memory access pattern that attackers can manipulate to achieve arbitrary code execution. The vulnerability's classification as a remote code execution flaw means that attackers do not require physical access to the target system, making it particularly concerning for enterprise environments where users frequently encounter external documents. The ZDI-CAN-13147 reference indicates this vulnerability was recognized and tracked by the Zero Day Initiative, highlighting its significance in the cybersecurity community.
Organizations using Foxit Reader should immediately implement mitigations including updating to the latest available version, implementing network-level protections such as web application firewalls, and deploying endpoint detection and response solutions to monitor for suspicious PDF processing activities. The vulnerability's exploitation requires user interaction, so security awareness training becomes crucial to prevent users from opening malicious documents. Additionally, organizations should consider implementing sandboxing mechanisms for PDF processing and restricting access to potentially harmful file types where possible. The remediation approach should also include monitoring for indicators of compromise such as unusual process execution patterns or network connections initiated by Foxit Reader during document processing, as these could signal exploitation attempts.