EUVD-2026-56458
GHSA-mqxf-72vh-q4mh
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
File-based exploit requires local execution by victim (AV:L, UI:R), no attacker privileges needed (PR:N), with full system compromise on successful exploitation (C:H/I:H/A:H).
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
AnalysisAI
Heap-based buffer overflow in Microsoft Office Excel enables local code execution when a user opens a specially crafted file, granting full confidentiality, integrity, and availability compromise of the affected system. The CVSS vector (AV:L/AC:L/PR:N/UI:R) confirms this is a document-triggered exploit requiring no attacker privileges but demanding victim interaction - a profile consistent with malicious email attachment or drive-by download campaigns. No public exploit code or CISA KEV listing has been identified at time of analysis, though Excel's ubiquity makes this a high-value target class.
Technical ContextAI
CWE-122 (Heap-based Buffer Overflow) identifies the root cause: Excel's parsing logic for a crafted spreadsheet file writes beyond the bounds of a heap-allocated buffer, enabling an attacker to corrupt adjacent heap memory and redirect execution flow. The attack surface is Excel's file parsing engine - a complex codebase historically affected by similar document-format memory corruption issues. The local attack vector (AV:L) in the CVSS vector reflects that exploitation occurs within the context of the victim process loading the malicious file, not via a network-exposed service. The MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-68807 is the authoritative source; no CPE strings were provided in the input, so exact affected version ranges cannot be confirmed independently.
RemediationAI
Apply the patch released by Microsoft via Windows Update or the Microsoft Update Catalog, referencing the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-68807 for the specific KB article and fixed build version. An exact patched version number was not included in the available input data; verify the precise fix version in the MSRC advisory before confirming remediation. As a compensating control, configure Protected View in Microsoft Office to open files from the internet and email attachments in read-only mode, which prevents automatic execution of file-parsing code paths that could trigger the overflow - note this requires user action to exit Protected View, creating a social-engineering bypass risk. Additionally, consider disabling macros via Group Policy and deploying Attack Surface Reduction rules to block Office applications from executing child processes (ASR rule ID: d4f940ab-401b-4efc-aadc-ad5f3c50688a). These mitigations reduce the attack surface but do not eliminate the underlying vulnerability.
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Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
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