CVE-2020-13560 in Foxit
Summary
by MITRE • 12/23/2020
A use after free vulnerability exists in the JavaScript engine of Foxit Software’s Foxit PDF Reader, version 10.1.0.37527. A specially crafted PDF document can trigger reuse of previously free memory which can lead to arbitrary code execution. An attacker needs to trick the user to open the malicious file to trigger this vulnerability. If the browser plugin extension is enabled, visiting a malicious site can also trigger the vulnerability.
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Analysis
by VulDB Data Team • 05/06/2026
This vulnerability represents a critical use after free condition within Foxit Software's PDF Reader JavaScript engine, specifically affecting version 10.1.0.37527 and potentially earlier releases. The flaw occurs when processing specially crafted PDF documents that contain malformed JavaScript code designed to exploit memory management weaknesses in the reader's engine. When the JavaScript engine encounters such malicious content, it executes a sequence of operations that result in previously allocated memory blocks being freed but subsequently accessed, creating a dangerous state where attackers can manipulate the program's execution flow.
The technical implementation of this vulnerability stems from improper memory management within the JavaScript interpreter component of the PDF reader. When processing certain PDF constructs, the engine fails to properly track object references and memory allocation states, allowing for situations where objects are deallocated while still referenced elsewhere in the execution path. This memory corruption condition provides attackers with opportunities to inject and execute arbitrary code with the privileges of the victim user, as the JavaScript engine operates within the same security context as the application itself. The vulnerability manifests through normal PDF document processing operations, making it particularly dangerous as users cannot easily distinguish between benign and malicious content without specialized analysis tools.
The operational impact of this vulnerability extends beyond simple exploitation scenarios, representing a significant threat to enterprise security environments where PDF documents are frequently exchanged and opened. Attackers can leverage this weakness through social engineering campaigns that trick users into opening malicious PDF files, or more sophisticated attacks that deliver malicious content through web browsers when the Foxit plugin extension is enabled. The attack surface expands significantly in environments where users regularly browse untrusted websites or receive PDF attachments from unknown sources, as the browser plugin extension creates additional vectors for exploitation without requiring user interaction beyond visiting a compromised website.
Mitigation strategies should focus on immediate software updates to patched versions that address the memory management flaws within the JavaScript engine. Organizations must implement comprehensive endpoint protection measures including sandboxing mechanisms and strict file type filtering to prevent automatic execution of potentially malicious PDF content. Network-level defenses such as web application firewalls and content inspection systems can help detect and block known attack patterns associated with this vulnerability. Security teams should also conduct regular vulnerability assessments targeting PDF processing components and establish incident response procedures specifically designed to handle use after free exploitation scenarios. The vulnerability aligns with CWE-416, which classifies use after free conditions as memory safety issues that can lead to arbitrary code execution, and represents a technique commonly documented in ATT&CK framework under T1059.007 for JavaScript-based execution methods.
The persistence of such vulnerabilities in commercial PDF readers highlights the ongoing challenges in securing complex document processing engines that must handle extensive formatting capabilities while maintaining memory safety. Regular security audits of third-party components, implementation of robust input validation mechanisms, and adherence to secure coding practices remain essential defensive measures against similar memory corruption vulnerabilities that continue to affect enterprise applications and user-facing software products. Organizations should also consider implementing additional layers of protection such as privilege separation, memory protection features like DEP and ASLR, and user education programs to reduce the likelihood of successful exploitation through social engineering approaches.