CVE-2026-91794 in PDF Editor
Summary
by MITRE • 09/23/2026
An out-of-bounds write vulnerability exists in the PDF rendering process of Foxit PDF Editor/Reader due to insufficient consistency and boundary validation when processing malformed color space data, which may cause the program to crash and potentially lead to remote code execution.
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Analysis
by VulDB Data Team • 09/23/2026
The identified security flaw resides within the core PDF rendering engine of Foxit PDF Editor and Reader, specifically affecting how the application processes color space definitions embedded in Portable Document Format files. This vulnerability is classified as an out-of-bounds write, a critical memory corruption issue where data is written to a memory location beyond the boundaries of the intended buffer or array structure. The root cause lies in insufficient consistency checks and inadequate boundary validation mechanisms when parsing malformed or maliciously crafted color space metadata. In standard PDF processing workflows, color spaces define how colors are represented within the document, such as device-dependent models like RGB or CMYK, or device-independent models like Lab or ICC-based profiles. When a parser encounters these definitions, it must strictly validate that all referenced indices and data structures fall within pre-allocated memory limits to prevent buffer overflows.
In this specific instance, the vulnerability arises because the software fails to adequately verify the integrity of color space objects before attempting to render them. An attacker can construct a PDF file containing specially crafted color space definitions where parameters such as array lengths or index references exceed the expected bounds defined by the application's internal memory allocation routines. When the rendering engine processes this malformed data, it attempts to write information into memory locations that are not allocated for that specific operation. This results in overwriting adjacent memory structures, which can corrupt critical program state variables, function return addresses, or other control flow mechanisms within the process space.
The operational impact of this vulnerability is severe due to its potential for remote code execution. While a simple crash resulting from an access violation might seem like a denial-of-service issue, out-of-bounds writes are particularly dangerous because they allow attackers to manipulate memory contents arbitrarily. By carefully crafting the payload and controlling which bytes are overwritten, a malicious actor can hijack the control flow of the application. This capability enables the execution of arbitrary code with the privileges of the user running the PDF viewer or editor. Given that Foxit products are widely used in enterprise environments for viewing sensitive documents, this vulnerability poses a significant risk to organizational security posture if users open untrusted PDF files received via email or downloaded from compromised websites.
From an industry standards perspective, this flaw aligns with Common Weakness Enumeration identifier CWE-787, which denotes out-of-bounds write vulnerabilities caused by improper validation of array indices or buffer sizes. Furthermore, the exploitation technique falls under MITRE ATT&CK tactic T1203, specifically referencing exploit for public vulnerability, as attackers leverage known weaknesses in widely deployed software to gain initial access. The lack of robust boundary checks during the parsing phase highlights a deficiency in secure coding practices related to input validation and memory management safety.
To mitigate this risk, users are strongly advised to update Foxit PDF Editor and Reader to the latest version released by the vendor, which includes patches addressing these specific boundary validation failures. Organizations should implement strict email filtering policies to block or quarantine attachments containing suspicious PDF files until they can be scanned with updated security tools. Additionally, enabling sandboxing features within the operating system can limit the impact of any potential exploitation by restricting the application's access to critical system resources and memory regions. Regular vulnerability assessments and adherence to secure development lifecycle principles that emphasize rigorous input validation are essential for preventing similar memory corruption issues in future software releases.