Description

A heap-based out-of-bounds write vulnerability exists in Foxit PDF Editor/Reader’s rendering of Circle annotations with malformed Cloudy appearance streams in specially crafted PDF files. Insufficient validation of the appearance geometry can result in memory corruption and application crashes.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-09-23T08:17:12.477Z",
  "pubdate": "2026-09-23T08:17:12.477Z",
  "executiveSummary": "This vulnerability is a heap-based out-of-bounds write flaw affecting Foxit PDF Editor and Reader.\nThe issue resides within the application's rendering engine, specifically regarding the processing of Circle annotations that incorporate malformed Cloudy appearance streams.\nSuccessful exploitation allows a remote attacker to induce memory corruption, which typically results in an application crash or potentially arbitrary code execution if the heap state is manipulated effectively.\nThe vulnerability is triggered by convincing a user to open a specially crafted malicious PDF file.\nThere are no specific authentication or privilege requirements for the attacker, as the vulnerability is triggered via the client-side parsing of the PDF structure.\nThe impact is significant, as it could compromise the integrity and availability of the host application, posing a substantial risk to end-user systems.",
  "technicalDetails": "The vulnerability originates from an insufficient validation process during the parsing and rendering of appearance streams associated with Circle annotations in Foxit PDF products.\nSpecifically, the rendering engine fails to perform proper bounds checking when calculating the geometry of 'Cloudy' appearance streams defined within the PDF structure.\nWhen the application attempts to render these malformed annotations, it calculates memory offsets based on the provided geometry parameters; if these parameters contain anomalous values, the application performs a heap-based write operation outside of the allocated buffer boundaries.\nThe exploitation flow begins when an attacker distributes a crafted PDF file to a target user. Upon opening the file, the Foxit rendering component encounters the malformed Cloudy annotation. The internal geometry calculation logic fails to sanitize the input data, leading to an integer overflow or underflow that results in an incorrect heap memory address being targeted during the memory write operation.\nThis out-of-bounds write primitive allows for the corruption of adjacent heap metadata or adjacent heap-allocated objects. By carefully crafting the PDF structure, an attacker may influence the heap layout to facilitate the overwriting of sensitive control structures or function pointers.\nIf the attacker successfully overwrites critical application data structures, they may achieve arbitrary code execution within the context of the user running the application. Even in the absence of code execution, the corruption leads to an unhandled exception and a subsequent application crash, representing a denial-of-service condition.\nThe vulnerability is dependent on the application's PDF parsing engine, which processes complex objects dynamically. Because the parsing happens at the application layer, this flaw does not require pre-existing authentication or specific system privileges to trigger; it relies entirely on the user-driven interaction of opening a malicious file.\nThe affected component is the rendering module responsible for processing PDF annotations, which necessitates continuous monitoring of input validation and rigorous bounds checking for all graphic parameters defined in the PDF specification."
}