CVE-2026-91808 in PDF Editor
Summary
by MITRE • 09/23/2026
A heap-based out-of-bounds read vulnerability exists in Foxit PDF Editor Reader’s handling of PDF image objects with inconsistent compression metadata. Insufficient validation during image decoding may result in an undersized buffer and an out-of-bounds read during rendering, causing an application crash.
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Analysis
by VulDB Data Team • 09/23/2026
The identified security flaw resides within the core image processing subsystem of Foxit PDF Editor Reader, specifically targeting the parsing logic for Portable Document Format (PDF) files that contain embedded raster images. This vulnerability is classified as a heap-based out-of-bounds read, which corresponds to CWE-125 in the Common Weakness Enumeration taxonomy. The root cause stems from an insufficient validation mechanism during the decoding phase of image objects where compression metadata is present but inconsistent or malformed. When the application processes these specific PDF structures, it fails to accurately calculate the required buffer size based on the declared dimensions and compression parameters provided by the document author. This miscalculation leads to the allocation of a memory buffer that is smaller than what is actually needed for safe rendering operations.
During the subsequent rendering process, the software attempts to read pixel data or compressed streams from this undersized heap-allocated buffer without performing adequate boundary checks before accessing memory locations beyond its allocated limits. This out-of-bounds access allows the application to read arbitrary memory contents that do not belong to the image object being processed. While the immediate observable symptom is an application crash due to a segmentation fault or similar exception triggered by invalid memory access, such vulnerabilities are frequently precursors to more severe exploitation scenarios. In many cases, reading beyond buffer boundaries can leak sensitive information from adjacent heap structures, potentially exposing cryptographic keys, session tokens, or other private data stored in the process memory space.
From an operational impact perspective, this vulnerability primarily affects the stability and availability of the Foxit PDF Editor Reader application. An attacker could craft a malicious PDF file containing specially constructed image objects with inconsistent compression metadata to trigger this condition remotely via email attachments or web-based document viewers that utilize the vulnerable component. Successful exploitation results in denial of service through application termination, which disrupts user workflows and can cause data loss if unsaved work is present. Although heap out-of-bounds reads are less commonly associated with direct code execution compared to write variants, they remain significant security risks because modern memory corruption exploits often leverage information disclosure techniques to bypass mitigations such as Address Space Layout Randomization before achieving arbitrary code execution through subsequent vulnerabilities or advanced exploitation chains.
This vulnerability aligns with the MITRE ATT&CK framework under technique T1203, which covers Exploitation for Client Execution, specifically when triggered by user interaction with a malicious document. It also relates to CWE-787 in contexts where boundary checks are omitted during pointer arithmetic operations common in C and C++ based applications like PDF parsers. To mitigate this risk, users should ensure that Foxit PDF Editor Reader is updated to the latest version released by the vendor, which includes patches for input validation logic within the image decoding routines. Administrators should enforce strict policies regarding the opening of untrusted documents and consider deploying application whitelisting or sandboxing solutions to limit the potential impact of any successful exploitation attempts. Regular security updates and adherence to secure coding practices that emphasize rigorous bounds checking during memory allocation and access are critical defenses against this class of heap-based vulnerabilities.