Description

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

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.5",
  "pubDate": "2026-08-11T17:19:10.643Z",
  "pubdate": "2026-08-11T17:19:10.643Z",
  "executiveSummary": "An out-of-bounds read vulnerability exists in Microsoft Office Excel, which allows an unauthorized remote attacker to disclose sensitive information over a network. The flaw resides within the data processing logic of the affected software, specifically when parsing specially crafted files or network streams. Successful exploitation of this vulnerability can lead to the unauthorized disclosure of memory contents, potentially exposing confidential data such as credentials, application state, or heap memory structures. This information disclosure could facilitate subsequent attacks by providing the adversary with critical reconnaissance details. The attack requires minimal interaction from a user, typically involving the opening of a malicious document or processing of compromised network content. Risk implications include the compromise of data confidentiality within enterprise environments utilizing vulnerable versions of Microsoft Office Excel. There are no elevated privilege requirements for the threat actor to initiate the attack, as the vulnerability can be triggered via unauthenticated network vectors or standard file handling routines.",
  "technicalDetails": "The vulnerability is fundamentally rooted in an out-of-bounds read flaw within Microsoft Office Excel. This memory safety issue occurs when the application fails to adequately validate boundary constraints or size parameters while processing specific file structures or data records. During parsing operations, the underlying component reads memory past the designated buffer boundary due to improper indexing or miscalculated offset values.\nThe vulnerable component is the file parser module responsible for handling legacy or modern spreadsheet formats within Microsoft Office Excel. When a user opens a maliciously crafted document or accesses a compromised network resource containing malformed data, the application initiates parsing routines that consume the malicious input. The payload behavior involves manipulating length fields or header metadata to induce the parser into reading contiguous memory allocations beyond the allocated buffer boundaries.\nThe attack flow proceeds as follows: First, the unauthorized attacker crafts a specialized file or network payload designed to exploit the boundary checking failure. Second, the victim opens the file or interacts with the malicious resource using Microsoft Office Excel. Third, the parsing engine processes the malformed structures, triggering the out-of-bounds read condition during memory operations. Fourth, the application inadvertently captures or exposes adjacent memory contents, which may be reflected back to the attacker or inadvertently logged depending on the specific execution context and error-handling routines.\nExploitation does not require authentication or elevated privileges, operating within the security context of the locally logged-in user or the network service handling the request. Network exposure is a factor if the application processes untrusted streams directly over a network interface or via automated server-side rendering pipelines. The primary post-exploitation impact is unauthorized information disclosure, as the read primitive allows the retrieval of sensitive stack or heap data, bypassing standard memory isolation mechanisms without causing an immediate application crash."
}