CVE-2021-27264 in PhantomPDF
Summary
by MITRE • 03/30/2021
This vulnerability allows remote attackers to disclose sensitive information on affected installations of Foxit PhantomPDF 10.1.0.37527. 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 U3D objects embedded in PDF files. The issue results from the lack of proper validation of user-supplied data, which can result in a read past the end of an allocated object. An attacker can leverage this in conjunction with other vulnerabilities to execute arbitrary code in the context of the current process. Was ZDI-CAN-12291.
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Analysis
by VulDB Data Team • 04/07/2021
CVE-2021-27264 represents a critical information disclosure vulnerability affecting Foxit PhantomPDF version 10.1.0.37527 that stems from improper handling of U3D objects within PDF documents. This vulnerability resides in the software's object parsing mechanism where insufficient input validation allows maliciously crafted U3D data to trigger memory access violations. The flaw manifests as a buffer over-read condition when the application attempts to process embedded U3D (Universal 3D) objects that contain malformed or oversized data structures. According to CWE-125, this vulnerability maps directly to an out-of-bounds read scenario where the application fails to properly bounds-check user-supplied data during object deserialization. The security implications extend beyond simple information disclosure as this memory access violation can potentially be leveraged to extract sensitive memory contents including stack canaries, heap metadata, or other process-specific information that could aid in more sophisticated exploitation techniques.
The exploitation of this vulnerability requires user interaction through either visiting a malicious webpage that loads a crafted PDF or opening a specially crafted PDF file containing the malicious U3D object. This attack vector aligns with ATT&CK technique T1203, which describes social engineering tactics used to gain initial access to systems through deceptive content delivery. The vulnerability's impact is particularly concerning because U3D objects are commonly used in PDF documents for 3D content rendering, making this attack surface accessible through normal PDF viewing activities. When a user opens or previews a PDF containing the malformed U3D object, the application's parsing routine fails to validate the object boundaries, leading to memory corruption that can be leveraged to disclose memory contents. This behavior demonstrates a classic case of insufficient input validation that violates security principles outlined in the OWASP Top Ten and the CERT Secure Coding Standards.
The operational impact of this vulnerability extends beyond immediate information disclosure to create potential pathways for privilege escalation and arbitrary code execution. While the primary effect is memory disclosure, the underlying buffer over-read condition creates opportunities for attackers to manipulate the application's execution flow through information leakage. Attackers can potentially use the disclosed memory information to bypass security mitigations such as address space layout randomization or stack canaries. The vulnerability's classification as a read past the end of an allocated object indicates that the application's memory management routines lack proper bounds checking mechanisms that should be implemented according to secure coding practices. This type of vulnerability often serves as a stepping stone in exploit chains where initial information disclosure is used to gather intelligence before attempting more sophisticated attacks like remote code execution.
Mitigation strategies for CVE-2021-27264 should focus on both immediate patching and defensive measures to protect against exploitation attempts. The primary recommendation is to upgrade to Foxit PhantomPDF version 10.1.0.37528 or later, which includes proper bounds checking for U3D object parsing. Organizations should also implement defensive measures such as PDF content filtering that blocks or sanitizes U3D objects before they reach end-user systems. Network-level protections including web application firewalls and content inspection systems can help detect and block malicious PDF files containing crafted U3D objects. Additionally, user education and awareness programs should emphasize the dangers of opening untrusted PDF files, particularly those containing embedded multimedia content. The vulnerability demonstrates the importance of proper input validation and memory safety practices, aligning with security frameworks such as the NIST Cybersecurity Framework and ISO 27001 security controls that emphasize the need for secure software development practices. Organizations should also consider implementing sandboxing techniques for PDF processing to limit the potential impact of successful exploitation attempts.