EUVD-2026-56456
GHSA-fg32-39rc-x8mq
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
File must be opened locally by the user (AV:L, UI:R); no attacker credentials needed (PR:N); heap overflow yields full code execution (C:H/I:H/A:H) within the user's process scope (S:U).
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 victim opens a specially crafted Excel file. The attack requires no privileges from the attacker but does require user interaction - consistent with a malicious document delivery vector - and carries high impact across confidentiality, integrity, and availability. No active exploitation (KEV) or public exploit code has been identified in the provided intelligence at time of analysis.
Technical ContextAI
CWE-122 (Heap-based Buffer Overflow) describes a write operation that exceeds the bounds of a heap-allocated memory region. In Microsoft Excel, this class of flaw typically arises during parsing of complex file structures (e.g., XLSB, XLS, or XLSX record formats), where field length values from the file are trusted without sufficient bounds validation. The CVSS vector AV:L/UI:R confirms the attack surface is a locally-opened file - the application reads attacker-controlled bytes and writes beyond a heap buffer, corrupting adjacent allocations and enabling arbitrary code execution. The affected product is Microsoft Office Excel; precise version ranges are not specified in the available CPE data, and the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-68800 should be consulted for confirmed build ranges.
RemediationAI
Apply the Microsoft security update published through the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-68800 - the exact patched version is not confirmed in the available input data and must be verified there directly. As a compensating control prior to patching, organizations can configure Protected View to open files from the internet or email attachments in a sandboxed read-only mode, which prevents automatic macro and parser execution on untrusted documents. Additionally, Microsoft's Attack Surface Reduction (ASR) rules - specifically the rule blocking Office applications from creating child processes - can limit post-exploitation lateral movement even if the overflow is triggered. Disabling file type associations for legacy Excel formats (XLS, XLSB) in high-risk environments reduces the attack surface at the cost of compatibility with older spreadsheets.
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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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