EUVD-2026-44040
GHSA-hr7p-25v4-pxc7
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 prior privileges needed (PR:N); memory-corruption code execution yields full user-context CIA impact.
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
Stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
AnalysisAI
Local code execution in Microsoft Excel (and the broader Office family through Microsoft 365 Apps, Office 2019/2021/2024 LTSC, Office for Mac, and Office Online Server) arises from a stack-based buffer overflow (CWE-121) triggered when a user opens a maliciously crafted spreadsheet. An attacker who convinces a victim to open the file runs arbitrary code in the security context of the current user, with high impact to confidentiality, integrity, and availability. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a user to open an attacker-supplied malicious spreadsheet file in a vulnerable Excel/Office build - the CVSS UI:R and AV:L metrics confirm local vector plus mandatory user interaction, so this cannot be triggered remotely without victim action. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score is 7.8 (High) with vector AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - meaning code execution is local, low-complexity, requires no privileges but does require user interaction (opening a file), with full CIA impact in the user's context. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker emails a crafted .xlsx/.xls spreadsheet (or hosts it for download) to a target and uses social engineering to get the victim to open it in a vulnerable Excel/Office build. Parsing the malformed data overflows a stack buffer and executes attacker code in the user's context, giving the attacker a foothold for credential theft or lateral movement. … |
| Remediation | Patch available per vendor advisory - apply Microsoft's security update for each affected channel via the MSRC update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55899, ensuring Click-to-Run/Microsoft 365 Apps auto-update is enabled and that LTSC/MSI builds, Office for Mac, and Office Online Server all receive their respective updates (exact patched build numbers are listed in the advisory and were not provided here). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all Microsoft Excel and Office product installations across your environment (Office 365, Office 2019, Office 2021, Office 2024 LTSC, Office for Mac, and Office Online Server) and assess patch readiness; coordinate deployment planning with IT operations. …
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Same weakness CWE-121 – Stack-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
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