What is the CVSS score of CVE-2025-21390?

CVE-2025-21390 has a CVSS 3.1 base score of 7.8 (High). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.3%.

How to fix or mitigate CVE-2025-21390?

Within 7 days: Identify all affected systems and apply vendor patches promptly. If patching is delayed, consider network segmentation to limit exposure.

Excel CVE-2025-21390

HIGH

Heap-based Buffer Overflow (CWE-122)

2025-02-11 secure@microsoft.com

RCE Buffer Overflow Heap Overflow Microsoft 365 Apps Excel Office Office Long Term Servicing Channel Office Online Server

7.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-122 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V15 - Secure Coding and Architecture Heap buffer bounds checking MITRE ATT&CK 1 technique across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 7.8 (HIGH). Attack characteristics: local attack vector, low complexity, no privileges required, user interaction required. EPSS exploitation probability: 0.29%.
Exploit ScenarioDerived	Successful exploitation could compromise the high-severity affected system.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 28, 2026

Microsoft Excel Remote Code Execution Vulnerability. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified under CWE-122. Affected products include: Microsoft 365 Apps, Microsoft Excel, Microsoft Office, Microsoft Office Long Term Servicing Channel, Microsoft Office Online Server.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.8 HIGH

AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Patch released

Mar 28, 2026 - 18:26 nvd

Patch available

CVE Published

Feb 11, 2025 - 18:15 nvd

HIGH 7.8

DescriptionCVE.org

Microsoft Excel Remote Code Execution Vulnerability

Executive ViewAI

Why It Matters

CVE-2025-21390 presents notable security risk, a heap-based buffer overflow vulnerability rated CVSS 7.8. Exploitation could allow attackers to corrupt memory, crash the application, or potentially execute arbitrary code. A patch is available and should be applied as part of regular vulnerability management.

Business Impact: High

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Enable ASLR and DEP where available; (2) Implement network segmentation; (3) Monitor for exploitation indicators.

Threat Intelligence Overview

EPSS Score

0.3%

Top 47% exploitable

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 0.3%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Small

Automatable· derived

Human Impact

High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +39

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Heap Overflow HIGH

A heap overflow occurs when a program writes data beyond the bounds of a buffer allocated in the heap memory region.

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)CVE.org

cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x64:*

cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x86:*

cpe:2.3:a:microsoft:excel:2016:*:*:*:*:*:x64:*

cpe:2.3:a:microsoft:excel:2016:*:*:*:*:*:x86:*

cpe:2.3:a:microsoft:office:2019:*:*:*:*:*:x64:*

cpe:2.3:a:microsoft:office:2019:*:*:*:*:*:x86:*

cpe:2.3:a:microsoft:office_long_term_servicing_channel:2021:*:*:*:*:*:x64:*

cpe:2.3:a:microsoft:office_long_term_servicing_channel:2021:*:*:*:*:*:x86:*

cpe:2.3:a:microsoft:office_long_term_servicing_channel:2021:*:*:*:*:macos:*:*

cpe:2.3:a:microsoft:office_long_term_servicing_channel:2024:*:*:*:*:*:x64:*

cpe:2.3:a:microsoft:office_long_term_servicing_channel:2024:*:*:*:*:*:x86:*

cpe:2.3:a:microsoft:office_long_term_servicing_channel:2024:*:*:*:*:macos:*:*

cpe:2.3:a:microsoft:office_online_server:*:*:*:*:*:*:*:*

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References

Advisories & patches

PATCH https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21390

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