CVE-2026-91815 in PDF Editor
Summary
by MITRE • 09/23/2026
Foxit PDF Editor/Reader does not perform sufficient verification of the JPEG2000 image metadata in the PDF file, which leads to out-of-bounds write in the heap buffer during decoding, potentially causing the program to crash and introducing the risk of arbitrary code execution.
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Analysis
by VulDB Data Team • 09/23/2026
The vulnerability identified in Foxit PDF Editor and Reader stems from a critical failure in input validation mechanisms when processing JPEG2000 image metadata embedded within Portable Document Format files. As a specialized document viewer, Foxit relies on complex rendering engines to interpret various media types, including the high-compression JPEG2000 standard. The core technical flaw lies in the insufficient verification of metadata fields associated with these images prior to their allocation and decoding processes. Specifically, when an attacker crafts a malicious PDF file containing a JPEG2000 image with manipulated or malformed header information, the application fails to adequately validate the dimensions, bit depth, or other structural parameters defined within that metadata. This lack of rigorous boundary checking allows for a discrepancy between the expected memory allocation size and the actual data volume processed during the decoding phase.
This validation gap directly facilitates an out-of-bounds write vulnerability in the heap buffer. During the execution of the image decoding routine, the software allocates a specific amount of contiguous memory based on potentially trusted but unverified metadata values. However, because the input is not sufficiently sanitized or validated against realistic constraints, the decoder attempts to write pixel data beyond the allocated boundaries of this heap-allocated buffer. This overflow overwrites adjacent memory structures, which may include critical control flow data such as function pointers, return addresses, or other object headers stored in close proximity within the heap space. The immediate operational impact of this corruption is often a program crash due to segmentation faults or access violations when the corrupted memory is accessed later by the application logic.
Beyond simple denial-of-service conditions manifested through crashes, the primary risk associated with this vulnerability is arbitrary code execution. By carefully crafting the malicious PDF payload, an attacker can control the data written into the out-of-bounds region of the heap buffer. This capability allows for precise manipulation of memory contents to hijack the program's execution flow. Through techniques such as heap spraying or targeted overwrites of function pointers, a remote attacker could potentially execute arbitrary shellcode within the context of the user running Foxit PDF Editor or Reader. Given that these applications are frequently used in enterprise environments where users open documents from various sources, this presents a significant attack vector for drive-by downloads and initial access campaigns targeting organizational networks.
From a classification perspective, this vulnerability aligns with CWE-120 Buffer Copy without Checking Size of Input, which describes the classic buffer overflow scenario resulting from inadequate bounds checking during data copying operations. Furthermore, it relates to CWE-20 Improper Input Validation, as the root cause is the failure to verify that incoming JPEG2000 metadata conforms to expected structural and dimensional constraints before processing. In terms of offensive security frameworks, this vulnerability supports techniques found in MITRE ATT&CK under T1203 Exploitation for Client Execution, where attackers leverage vulnerabilities in client-side applications like document viewers to gain initial footholds on target systems without requiring user interaction beyond opening the file.
Mitigation strategies must address both immediate remediation and long-term defensive posture improvements. The most effective solution is to apply vendor-provided patches or updates that rectify the input validation logic within the JPEG2000 decoding module, ensuring strict adherence to memory allocation limits based on verified metadata. Organizations should prioritize updating Foxit PDF applications across all endpoints to eliminate exposure to this specific exploit chain. Additionally, implementing application whitelisting and restricting script execution can help mitigate the impact if a successful exploitation attempt occurs by preventing arbitrary code from running in untrusted contexts. Network-level controls such as deep packet inspection or sandboxing of incoming documents before they reach end-user devices also serve as valuable compensating controls to detect and block malicious PDF files containing malformed JPEG2000 streams prior to local processing.