CVE-2020-15637 in PhantomPDF
Summary
by MITRE
This vulnerability allows remote attackers to disclose sensitive information on affected installations of Foxit PhantomPDF 9.7.1.29511. 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 SetLocalDescription method. By performing actions in JavaScript, an attacker can cause a pointer to be reused after it has been freed. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of the current process. Was ZDI-CAN-10972.
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Analysis
by VulDB Data Team • 05/06/2026
This vulnerability in Foxit PhantomPDF version 9.7.1.29511 represents a critical memory safety issue that enables remote information disclosure and potential code execution. The flaw exists within the SetLocalDescription method of the PDF rendering engine, where improper memory management allows for use-after-free conditions. Attackers can exploit this vulnerability by crafting malicious JavaScript code that triggers the vulnerable method, causing a pointer to be accessed after it has been deallocated from memory. This type of vulnerability falls under the CWE-416 category for use-after-free conditions, which is a well-documented class of memory corruption vulnerabilities that frequently lead to arbitrary code execution. The vulnerability requires user interaction to be exploited, meaning victims must visit a malicious webpage or open a specially crafted PDF file containing the malicious JavaScript payload. This makes the attack vector particularly dangerous as it can be delivered through web-based attacks or malicious documents that users might legitimately open. The memory corruption occurs during JavaScript execution within the PDF viewer context, allowing attackers to manipulate memory pointers and potentially execute arbitrary code with the privileges of the running process.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass full system compromise in many scenarios. When an attacker successfully exploits the use-after-free condition, they can leverage the memory corruption to overwrite critical function pointers or execute shellcode within the context of the PhantomPDF process. This presents a significant threat to enterprise environments where PDF viewers are frequently used to process documents from untrusted sources. The vulnerability's classification as a remote attack means that exploitation can occur without requiring physical access to the target system, making it particularly dangerous for organizations with remote workers or those that frequently exchange PDF documents with external parties. The fact that this vulnerability was tracked as ZDI-CAN-10972 indicates it was recognized by the Zero Day Initiative security research team, highlighting its significance in the cybersecurity community. Organizations using Foxit PhantomPDF 9.7.1.29511 are at risk of targeted attacks where adversaries craft malicious PDF documents specifically designed to exploit this memory corruption flaw.
Mitigation strategies for this vulnerability should focus on immediate patching of the affected software version and implementation of additional security controls. The primary recommendation is to update to a patched version of Foxit PhantomPDF that addresses the memory management issue in the SetLocalDescription method. Organizations should also implement web filtering solutions and email security controls to prevent users from accessing malicious PDF files or web pages containing the exploit code. Browser-based security measures such as sandboxing and content security policies can provide additional protection layers against exploitation attempts. Network monitoring should be enhanced to detect unusual JavaScript activity or attempts to access memory addresses that might indicate exploitation attempts. From an operational security perspective, organizations should conduct regular security assessments of their PDF handling processes and implement least-privilege principles for PDF viewer applications. The vulnerability demonstrates the importance of proper memory management in client-side applications and highlights the need for regular security updates and vulnerability management processes. This case also emphasizes the value of security research initiatives like the Zero Day Initiative in identifying and reporting critical vulnerabilities before they can be widely exploited in the wild.