EUVD-2026-44206
GHSA-2xhx-8hwj-hj2c
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
File-borne client-side RCE: AV:L and UI:R because the victim must open a crafted file, PR:N as no auth is needed, and C/I/A:H reflecting full code execution in the user's context.
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
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
AnalysisAI
Arbitrary code execution in Microsoft Office Excel arises from a heap-based buffer overflow (CWE-122) that an attacker triggers when a victim opens a maliciously crafted spreadsheet, running code in the security context of the current user. The flaw spans a broad Office footprint including Microsoft 365 Apps for Enterprise, Excel 2016, Office 2019, Office LTSC 2021/2024, the macOS Office editions, and Office Online Server. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the victim to open a specially crafted Excel spreadsheet in an affected Office build (UI:R in the CVSS vector) - this user-interaction requirement is the key limiting factor and means the attack cannot succeed without social engineering or a lured file open. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H, base 7.8) describes a client-side, user-interaction-dependent flaw: no privileges are required (PR:N) but the victim must open a malicious file (UI:R), which is the primary factor limiting mass exploitation and keeping the score at High rather than Critical. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker emails a finance employee a crafted .xlsx/.xls spreadsheet themed as an invoice or report; when the victim opens it in Excel, the malformed content triggers the heap overflow and executes attacker code in the user's context, establishing a foothold for data theft or ransomware staging. The AV:L/AC:L/UI:R vector means the attack is low-complexity once the file is opened but wholly dependent on that user action. … |
| Remediation | Apply the Microsoft security update for CVE-2026-55131 across all affected Office channels; the input confirms a patch is available from the vendor, so this is the primary and preferred fix - Patch available per vendor advisory. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all systems running Microsoft Excel 2016, Microsoft 365 Apps for Enterprise, Office 2019, Office LTSC 2021, Office LTSC 2024, macOS Office editions, or Office Online Server, and assess internal file-sharing practices and user email attachment handling. …
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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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