CVE-2026-50678 in Office
Summary
by MITRE • 07/14/2026
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 07/14/2026
A heap-based buffer overflow vulnerability exists in Microsoft Office Excel that enables unauthorized attackers to achieve local information disclosure through crafted malicious files. This vulnerability stems from improper memory management within the spreadsheet application's handling of specific data structures, particularly when processing malformed or specially constructed excel files. The flaw occurs during the parsing of certain worksheet elements where insufficient bounds checking allows an attacker to write beyond allocated heap memory regions. When Excel attempts to process these malicious inputs, it overflows adjacent memory blocks, potentially exposing sensitive data from other variables or program structures stored in the same memory allocation areas. The vulnerability is classified as a heap-based buffer overflow which represents a specific type of memory corruption issue that can lead to information disclosure and may potentially be leveraged for more severe attacks if combined with other exploitation techniques.
The technical implementation of this vulnerability involves the manipulation of Excel's internal data structures during file parsing operations, where attackers craft malicious spreadsheet files containing oversized or malformed elements that trigger the buffer overflow condition. When the vulnerable application processes these files, it fails to properly validate input boundaries before copying data into heap-allocated buffers. This specific flaw allows for information disclosure rather than direct code execution, though it represents a significant security risk as it can expose sensitive memory contents including credentials, encryption keys, or other confidential data that may be stored in adjacent memory locations. The vulnerability's impact is constrained to local information disclosure scenarios where an attacker must already have the ability to execute malicious files on the target system, typically through social engineering attacks or exploitation of other initial access vectors.
The operational implications of this vulnerability extend beyond simple information disclosure as it represents a foothold that could enable further attack progression within compromised environments. Attackers can potentially use this vulnerability to gather intelligence about running processes, memory layouts, or system configurations that might aid in subsequent exploitation attempts. The nature of heap-based buffer overflows makes them particularly dangerous because they often result in partial information leakage rather than complete system compromise, yet this partial disclosure can provide attackers with valuable insights into application behavior and memory organization. Security professionals should consider this vulnerability as part of broader threat modeling exercises, particularly when evaluating systems where Excel files are regularly processed or where sensitive data might be present in memory during spreadsheet operations.
Mitigation strategies for this heap-based buffer overflow vulnerability should focus on both immediate protective measures and long-term architectural improvements. Microsoft recommends applying the latest security updates and patches to address known vulnerabilities, as these typically contain fixes that implement proper bounds checking and memory management protections. Organizations should also implement strict file validation procedures for Excel files received from external sources, including sandboxed processing environments where potentially malicious content can be analyzed without risking primary systems. Network security controls such as email filtering and web application firewalls can help prevent initial delivery of malicious files, while endpoint protection solutions should include behavioral monitoring to detect anomalous spreadsheet processing activities. The vulnerability aligns with common weakness enumeration cw 121 which specifically addresses buffer overflow conditions in heap memory management, and may correspond to attack techniques described in the attack tree framework under information gathering and reconnaissance activities that could lead to more serious exploitation attempts.