CVE-2026-91810 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 malformed PDF image masks. Inconsistent image metadata may cause incorrect alpha-channel processing during rendering, resulting in an out-of-bounds read and application crash.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 09/23/2026
The identified security flaw resides within the core rendering engine of Foxit PDF Editor and Reader, specifically affecting the subsystem responsible for parsing and displaying image mask data structures embedded within Portable Document Format files. 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 lies in an inconsistency between the declared dimensions or metadata of an image mask and its actual allocated memory buffer size during the rendering process. When the application processes these malformed documents, it fails to perform adequate bounds checking before accessing pixel data for alpha-channel composition. This logical error allows the software to read from a memory location that falls outside the boundaries of the intended heap allocation, leading to unauthorized access of adjacent memory regions.
From an operational perspective, this vulnerability primarily manifests as a denial-of-service condition due to application instability. The incorrect alpha-channel processing triggers a crash when the renderer attempts to utilize invalid data pointers or corrupted pixel values during the compositing phase. While out-of-bounds reads are sometimes leveraged for information disclosure by leaking sensitive memory contents into the display buffer, in this specific context involving image rendering and mask handling, the immediate impact is system instability rather than direct code execution or data exfiltration. The attacker can trigger this condition simply by distributing a maliciously crafted PDF file that contains an image object with mismatched metadata fields, such as incorrect width, height, or bit-depth specifications relative to the actual stream length.
This type of vulnerability aligns with MITRE ATT&CK technique T1203, which covers Exploitation for Client Execution, particularly when delivered via social engineering tactics where a user is tricked into opening the malicious document. The lack of strict validation on image metadata allows an adversary to craft payloads that exploit the parser's assumptions about data integrity. Although the immediate result is often a crash, heap-based memory corruption vulnerabilities are frequently precursors to more severe exploits if additional conditions are met during future processing stages or in related components within the same application architecture.
To mitigate this risk, users should ensure they are running the latest version of Foxit PDF Editor and Reader where patches for image parsing logic have been applied. Administrators managing enterprise deployments should enforce strict update policies to guarantee that all client machines receive security fixes promptly. Additionally, implementing network-level filtering or endpoint detection systems capable of inspecting incoming PDF files for anomalous structures can provide an additional layer of defense against exploitation attempts. It is also advisable to disable JavaScript execution in untrusted documents and restrict the automatic loading of external resources to reduce the attack surface associated with document rendering engines.