EUVD-2026-35646
GHSA-9jgc-vw8w-2xv8
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
AnalysisAI
Local code execution in Microsoft Office Excel results from an integer underflow (CWE-122 heap-based) that allows an unauthorized attacker to run arbitrary code in the context of the user opening a crafted spreadsheet. The CVSS 7.8 score reflects local attack vector with required user interaction, and no public exploit identified at time of analysis. Microsoft (secure@microsoft.com) is the originating CNA, and the issue is tagged as a buffer/heap overflow class flaw.
Technical ContextAI
The underlying defect is an integer underflow (wrap-around) in Excel's parsing of file content, classified under CWE-122 (heap-based buffer overflow) - meaning a computed size or offset wraps below zero/around the integer range and is then trusted as a heap allocation or copy length. The tag set (Buffer Overflow, Heap Overflow) corroborates that the wrap leads to an undersized heap allocation followed by an oversized write, corrupting adjacent heap metadata or function pointers. Microsoft Office Excel is the affected product line; no CPE strings were provided in the input to pin exact SKUs (Office 2019, 2021, LTSC, or Microsoft 365 Apps), so the exact build matrix must be resolved via the MSRC advisory.
RemediationAI
Apply the Microsoft security update for Excel referenced in the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45469 as the primary fix; exact patched build numbers are published in that advisory and should be matched to your Office channel (Current, Monthly Enterprise, Semi-Annual, or LTSC). Until patching completes, reduce exposure by enforcing Protected View and Block Macros from the Internet via Group Policy or Intune, disabling automatic opening of attachments from external mail, and routing Office files through sandboxed previewers - trade-offs include user friction when legitimate external workbooks need elevated trust and the need to retrain users to use the 'Enable Editing' flow. Patch availability is per vendor advisory; pair the patch deployment with attack-surface reduction rules (e.g., ASR rule blocking Office child processes) to harden the post-exploit step.
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Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Heap Overflow
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External POC / Exploit Code
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