Description

Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "5.5",
  "pubDate": "2026-08-11T17:19:04.910Z",
  "pubdate": "2026-08-11T17:19:04.910Z",
  "executiveSummary": "This vulnerability is classified as an out-of-bounds read security flaw affecting Microsoft Office Excel. The primary impact of successful exploitation is local information disclosure, allowing an unauthorized attacker to read sensitive memory contents from the host system. The vulnerability resides within the Microsoft Office Excel component, posing a direct risk to confidentiality by potentially exposing uninitialized memory or sensitive data processed within the application context. Attack capabilities are constrained to local vector interactions, implying that an unauthorized threat actor must successfully execute localized maneuvers or entice a target user to interact with a maliciously crafted spreadsheet file. Exploitation requirements mandate that the victim opens a specifically constructed file within a vulnerable instance of Microsoft Office Excel, triggering the anomalous memory read condition. Given the nature of information disclosure vulnerabilities, successful exploitation can yield critical memory offsets or proprietary data leaks that could subsequently facilitate more complex attack chains, such as bypassing internal address space layout randomization protections if leveraged alongside other memory corruption vectors.",
  "technicalDetails": "The root cause of the vulnerability stems from insufficient boundary verification and bounds-checking logic within the Microsoft Office Excel file parsing engine when processing specific internal file structures or layout records. During the parsing phase of workbook components, the vulnerable component fails to adequately validate index offsets provided within the file against the allocated buffer sizes, leading directly to an out-of-bounds read condition. The affected component is the Microsoft Office Excel parser module responsible for interpreting proprietary or open file formats. The vulnerability can be exploited by an unauthorized attacker who delivers a maliciously crafted Excel document locally to the target system or via local attack vectors. Authentication requirements are non-existent locally since the application processes the file directly in the context of the user. Similarly, explicit privilege requirements are minimal, as standard user execution privileges are sufficient to trigger the parsing routine and subsequent memory read violation. Network exposure is negligible due to the local execution requirement, unless combined with secondary remote vectors such as email attachments or shared network drives where a user retrieves and opens the payload. The payload behavior involves the construction of malformed structural records designed to force the application parser to read past the designated buffer boundaries into adjacent memory regions. Step-by-step, exploitation occurs as follows: first, the attacker crafts a malicious spreadsheet containing corrupted length indicators or index fields; second, the target user opens this file utilizing Microsoft Office Excel; third, the application initializes the parsing routines for the embedded records; fourth, the parser reads data from memory addresses outside the legitimate buffer allocation due to missing bounds constraints; and fifth, the application inadvertently processes or exposes the out-of-bounds memory contents, potentially leaking sensitive stack or heap data back to the execution context or logging mechanisms. The post-exploitation impact is strictly confined to local information disclosure, potentially compromising sensitive application memory remnants, user data, or system variables residing near the target memory buffer."
}