CVE-2021-34851 in Foxit
Summary
by MITRE • 08/04/2021
This vulnerability allows remote attackers to execute arbitrary code on affected installations of Foxit PDF Reader 11.0.0.49893. 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-14016.
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Analysis
by VulDB Data Team • 08/08/2021
The vulnerability identified as CVE-2021-34851 represents a critical remote code execution flaw in Foxit PDF Reader version 11.0.0.49893 that demonstrates a classic improper input validation weakness. This vulnerability falls under the CWE-476 category of NULL Pointer Dereference, where the software fails to properly validate the existence of objects before attempting operations on them. The flaw specifically manifests within the Annotation object handling mechanism, which serves as a critical component in PDF document processing and user interaction elements.
The technical exploitation of this vulnerability requires user interaction through visiting a malicious webpage or opening a specially crafted malicious PDF file, making it a prime example of a client-side attack vector. When a user interacts with the malicious content, the PDF reader's annotation processing code attempts to perform operations on an object that has not been properly validated for existence, leading to a potential null pointer dereference condition. This condition can be leveraged by attackers to inject and execute arbitrary code within the context of the currently running process, effectively compromising the user's system.
From an operational impact perspective, this vulnerability presents a significant risk to organizations relying on Foxit PDF Reader for document processing and viewing. The requirement for user interaction reduces the attack surface compared to fully automated exploits, but the widespread use of PDF readers makes this vector highly attractive to threat actors. The code execution occurs in the context of the current process, meaning attackers could potentially escalate privileges or access sensitive system resources depending on the user's permissions and the system configuration. This vulnerability directly maps to ATT&CK technique T1059.007 for Command and Scripting Interpreter, specifically through the use of PDF-based attack vectors.
The exploitation process involves crafting a malicious PDF file containing specially formatted annotation objects that trigger the validation failure during processing. Attackers can leverage this weakness to deploy malware payloads, establish persistence mechanisms, or perform further reconnaissance activities within the compromised environment. Security professionals should note that this vulnerability represents a typical sandbox escape scenario where a legitimate application's processing logic is manipulated to execute unintended code paths. The ZDI-CAN-14016 reference indicates this issue was tracked by the Zero Day Initiative, highlighting its significance in the cybersecurity community and the need for immediate remediation.
Organizations should prioritize immediate patching of affected Foxit PDF Reader installations to prevent exploitation attempts. Additionally, implementing network-based security controls such as web application firewalls and content filtering solutions can help block malicious PDF content before it reaches end users. Regular security awareness training should emphasize the dangers of opening untrusted PDF files and visiting suspicious websites. System administrators should monitor for potential exploitation attempts through log analysis and endpoint detection systems, paying particular attention to unusual process execution patterns that might indicate successful exploitation of this vulnerability.