Description

A heap-based out-of-bounds write vulnerability exists in Foxit PDF Editor/Reader’s WebP image decoding due to improper handling of bitmap stride and target buffer formats. Successful exploitation could result in an application crash.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-09-23T08:17:12.247Z",
  "pubdate": "2026-09-23T08:17:12.247Z",
  "executiveSummary": "A heap-based out-of-bounds write vulnerability exists within the WebP image decoding module of Foxit PDF Editor and Foxit PDF Reader.\nThis vulnerability is classified as a memory corruption flaw, specifically an out-of-bounds write occurring during the process of rendering WebP image data.\nThe primary impact of successful exploitation is an application crash, which may result in a Denial of Service (DoS) condition.\nThe vulnerability originates from improper validation of bitmap stride calculations and target buffer formatting during the decoding process.\nExploitation does not inherently require authentication but typically necessitates that a victim opens a specially crafted PDF document containing a malicious WebP image.\nFrom an attacker's perspective, this flaw allows for the manipulation of heap memory structures. While currently identified as causing application instability, such vulnerabilities can sometimes be leveraged for arbitrary code execution if memory layout constraints are bypassed.\nRisk implications remain significant as PDF readers are common attack vectors for document-borne malicious payloads delivered via email or web downloads.\nUsers and administrators are advised to restrict the opening of untrusted PDF files and ensure the software is updated to the latest available vendor release to mitigate exposure.",
  "technicalDetails": "The vulnerability resides in the internal WebP decoding implementation of Foxit PDF Editor/Reader. The root cause is a failure to properly sanitize or validate the relationship between the bitmap stride and the allocated target buffer size when processing WebP image data.\nWhen the decoder attempts to map the decoded pixel data into the target buffer, it relies on stride information—the number of bytes occupied by a single row of pixels, including padding. If the provided WebP image header specifies a stride or image dimension that conflicts with the physical memory allocation on the heap, the decoding logic may calculate an incorrect offset.\nThe attack flow initiates when the application processes an image stream embedded within a PDF file. The malicious file contains a crafted WebP image that triggers the flawed decoding routine. As the decoder processes the pixel rows, it performs write operations based on the corrupted stride calculations.\nThis results in a heap-based out-of-bounds write, where the memory controller attempts to commit image data to an address range that falls outside the intended buffer boundary. In the current context, this memory corruption corrupts adjacent heap metadata or unrelated objects.\nThe lack of sufficient boundary checks between the decoded source data and the destination heap buffer allows the writing process to overwrite heap-resident structures. Because the heap is dynamic, this behavior is highly sensitive to the state of the heap allocator at the time of processing.\nThe primary observed outcome of this illegal memory access is a segmentation fault or a heap integrity violation, causing the application to terminate execution immediately to prevent further instability. This indicates that the application fails to handle malformed image streams gracefully during the transition from the decompression stage to the rendering stage.\nWhile the current impact is defined as an application crash, the vulnerability provides a primitive for memory corruption. If an attacker can predictably control the heap layout, they might achieve further exploitation primitives, such as the corruption of object pointers or control flow hijack, depending on the surrounding heap environment and the effectiveness of existing platform-level mitigations like Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP).\nNo specific authentication or elevated privileges are required beyond the ability to trigger the rendering of the malicious PDF within the context of the user running the application. The vulnerability is triggered locally by the software when it parses the malicious file content."
}