What is the CVSS score of CVE-2025-53770?

CVE-2025-53770 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 90.5%.

Is there a public PoC exploit available for CVE-2025-53770?

Yes, a public proof-of-concept exploit is available for CVE-2025-53770. Prioritise patching immediately. EPSS: 90.5%.

How to fix or mitigate CVE-2025-53770?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. Restrict deserialization to trusted data sources and implement integrity checks.

Sharepoint Server CVE-2025-53770

CRITICAL

Deserialization of Untrusted Data (CWE-502)

2025-07-20 secure@microsoft.com

Deserialization Microsoft Sharepoint Server

9.8

CVSS 3.1 · Vendor: microsoft

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Vulnerability Assessment

Weakness	CWE CWE-502 OWASP Top 10:2025 A08:2021 - Software and Data Integrity Failures ASVS 5.0 V10 - Malicious Code Integrity verification, supply chain security MITRE ATT&CK 2 techniques across 2 tactics: Execution, Initial Access 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	Critical risk (CVSS 9.8, EPSS 90.5%). SharePoint Server is widely deployed in enterprise environments for document management and collaboration. Unauthenticated RCE provides direct access to sensitive corporate data and Active Directory integration.
Exploit ScenarioDerived	An attacker sends crafted HTTP requests containing malicious serialized .NET objects to an on-premises SharePoint server. The server deserializes the payload, executing code that provides shell access to the server, from which the attacker accesses SharePoint content and pivots to Active Directory.

Emergency Immediate action required. Why: CRITICAL + in CISA KEV (actively exploited), no patch available.

Exploited in the wild (CISA KEV) No patch listed yet 90.5% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 26, 2026

Microsoft SharePoint Server contains a deserialization vulnerability allowing unauthenticated remote code execution over the network, with active exploitation confirmed and patches pending full release.

Earlier versions of this analysis (1)

v1 Mar 26, 2026 - 11:20 CVSS 9.8

A deserialization of untrusted data vulnerability in on-premises Microsoft SharePoint Server enables unauthenticated attackers to execute arbitrary code over the network. Microsoft confirmed active exploitation before a comprehensive update was available.

RemediationAI

Apply Microsoft's mitigation steps immediately. Install the comprehensive update when available. Restrict network access to SharePoint. Monitor for suspicious deserialization patterns in IIS logs.

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

The CWE-502 deserialization flaw allows unauthenticated attackers to send crafted serialized data to SharePoint Server, which deserializes it without proper validation, leading to arbitrary code execution in the SharePoint application context.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 9.8 CRITICAL

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

Primary rating from Vendor (microsoft) · only source for this CVE.

CVSS VectorVendor: microsoft

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Added to CISA KEV

Oct 27, 2025 - 17:12 cisa

CISA KEV

CIRCL Exploitation Confirmed

Oct 27, 2025 - 17:12 circl

CIRCL KEV

PoC Detected

Oct 27, 2025 - 17:12 vuln.today

Public exploit code

CVE Published

Jul 20, 2025 - 01:15 nvd

CRITICAL 9.8

DescriptionCVE.org

Deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an unauthorized attacker to execute code over a network. Microsoft is aware that an exploit for CVE-2025-53770 exists in the wild. Microsoft is preparing and fully testing a comprehensive update to address this vulnerability. In the meantime, please make sure that the mitigation provided in this CVE documentation is in place so that you are protected from exploitation.

Executive ViewAI

Why It Matters

Organizations using Deserialization of untrusted data in on-premises Microsoft SharePoint Server face critical risk from CVE-2025-53770, a insecure deserialization vulnerability rated CVSS 9.8. Insecure deserialization could allow attackers to execute arbitrary code by providing crafted serialized data. This vulnerability is actively exploited in the wild (KEV-listed) and requires immediate remediation. Immediate patching is required per CISA KEV mandate.

Business Impact: Severe

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Restrict deserialization endpoints; (2) Implement integrity checks on serialized data; (3) Use type-safe alternatives.

Threat Intelligence Overview

Threat Score

9.7/10

Composite threat intelligence

EPSS Score

90.5%

Top 0% exploitable

EUVD KEV

Listed

EU Exploited Vulnerability

CIRCL KEV

Listed

Community Exploited Vulnerability

Threat Intel

1 sources

Exploit

POC

Public exploit code exists

Data Quality

10 sources

Confidence: High

NVD

CVE.org

CISA KEV

EPSS CERT-EU POC (2) THREAT CIRCL

Exploit-DB

GitHub

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 CRITICAL

CISA KEV Yes

Public POC Yes

EPSS 90.5%

Patch available No

Active threat Yes

Deciding rule

CRITICAL + in CISA KEV (actively exploited), no patch available

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

Immediate

Exploitation· derived

Active

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact

Very High

Priority Score

235

Low Medium High Critical

KEV: +50

EPSS: +91

CVSS: +49

PoC: +20

Weaponized: +15

Threat intel: +10

Gov advisory: 0

Attack Technique

Insecure Deserialization CRITICAL

Insecure deserialization occurs when an application converts serialized data (a stream of bytes representing an object's state) back into a living object without proper validation.