Vulnerability report

Active exploitation observed Confirmed confidence In CISA KEV

CVE-2026-50522

Microsoft SharePoint Remote Code Execution Vulnerability

Microsoft SharePoint Enterprise Server 2016 · affected before 16.0.5561.1001

Watch CVE-2026-50522 Browse KEV feed
Severity
CVSS 9.8 · Critical
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
3.0%
First observed
25 Jul 2026
Last observed
26 Aug 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2026-50522 is an unauthenticated Microsoft SharePoint Remote Code Execution Vulnerability. Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a...

Is it exploited?

Yes. Previdian sensors observed exploitation attempts with confirmed confidence. Listed in CISA KEV. Also confirmed by third-party sources.

Who is affected?

Microsoft SharePoint Enterprise Server 2016 affected before 16.0.5561.1001.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

Microsoft SharePoint Remote Code Execution Vulnerability

Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.

Microsoft Affected
Microsoft SharePoint Enterprise Server 2016
Before 16.0.5561.1001
Microsoft Affected
Microsoft SharePoint Server 2019
Before 16.0.10417.20175
Microsoft Affected
Microsoft SharePoint Server Subscription Edition
Before 16.0.19725.20434
View vendor advisory (opens in new tab)
Published
14 Jul 2026
Exploitation Reported
21 Jul 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

microsoft cisa

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

watchTowr

Recorded 21 Jul 2026

A trusted third party reported exploitation.

Active exploitation observed

Previdian sensor

First observed 25 Jul 2026

Previdian first observed exploitation attempts targeting this vulnerability in our honeypot sensors.

Proof of concept available

GitHub

Recorded 20 Jul 2026

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
Rapid7 First 2026-07-17 18:18 UTC
watchTowr 2026-07-21 10:24 UTC
Daily CyberSecurity 2026-07-21 12:45 UTC
The Hacker News 2026-07-21 14:57 UTC
DarkWebInformer 2026-07-21 15:34 UTC
BleepingComputer 2026-07-21 20:06 UTC
All CISA Advisories 2026-07-22 12:00 UTC
CISA 2026-07-22 19:00 UTC
CVE 2026-07-22 21:02 UTC
CERT-EU 2026-07-23 09:13 UTC
Previdian Sensors 2026-07-25 11:11 UTC
The Shadowserver 2026-08-16 00:00 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

First-party evidence of exploitation activity

Previdian sensors recorded exploitation attempts targeting this vulnerability. The cards and chart show volume, unique attackers, and daily activity.

7

Attempts observed

2

Unique attacker IPs

2

Attacker countries

HK · NL

1

Sensors observed

CVE-2026-50522 exploitation attempts over the last 80 days

Daily events observed by Previdian sensors

Updated 11 Oct 2026

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24 Jul 9 Aug 25 Aug 10 Sep 11 Oct

First observed 25 Jul 2026 · Last observed 26 Aug 2026

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Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

Learn about Pro API access

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.8 Critical

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

EPSS

3.0%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Deserialization of Untrusted Data CWE-502

Recent mention · CERT-EU

2026-009: Critical Vulnerabilities in Microsoft SharePoint

[UPDATED] On 14 July 2026, Microsoft released security updates addressing critical remote code execution (RCE) vulnerabilities in Microsoft SharePoint Server. On 20 July 2026, WatchTowr identified a proof-of-concept exploit code and subsequently observed active exploitation of...

Read full advisory

All Mentions

Recent mention · CERT-EU

2026-009: Critical Vulnerabilities in Microsoft SharePoint

CERT-EU · 23 Jul 2026

[UPDATED] On 14 July 2026, Microsoft released security updates addressing critical remote code execution (RCE) vulnerabilities in Microsoft SharePoint Server. On 20 July 2026, WatchTowr identified a proof-of-concept exploit code and subsequently observed active exploitation of CVE-2026-50522, a vulnerability part of an ongoing series of actively exploited flaws affecting on-premise SharePoint Server instances, including CVE-2026-32201, CVE-2026-45659, CVE-2026-56164, and CVE-2026-58644. CERT-EU strongly recommends updating affected servers immediately, rotating credentials for any assets...

Recent mention · All CISA Advisories

CISA Adds Two Known Exploited Vulnerabilities to Catalog

All CISA Advisories · 22 Jul 2026

CISA has added two new vulnerabilities to its Known Exploited Vulnerabilities (KEV) Catalog, based on evidence of active exploitation.   CVE-2026-16232 Check Point SmartConsole Improper Authentication Vulnerability CVE-2026-50522 Microsoft SharePoint Deserialization of Untrusted Data Vulnerability These types of vulnerabilities are a frequent attack vector for malicious cyber actors and pose significant risks to the federal enterprise. Binding Operational Directive (BOD) 26-04: Prioritizing Security Updates Based on Risk establishes vulnerability management requirements for Federal...

Recent mention · BleepingComputer

Critical SharePoint RCE flaw exploited to steal machine keys

BleepingComputer · 21 Jul 2026

Hackers are actively exploiting the critical CVE-2026-50522 vulnerability in Microsoft SharePoint to steal machine keys and maintain access even after affected servers are patched. [...]

Recent mention · DarkWebInformer

Patching Is Not Enough: Critical SharePoint Deserialization RCE Under Active Exploitation (CVE-2026-50522)

DarkWebInformer · 21 Jul 2026

CVE-2026-50522 is a critical remote code execution vulnerability in on-premises Microsoft SharePoint Server, caused by deserialization of untrusted data (CWE-502).

Recent mention · The Hacker News

Critical SharePoint RCE CVE-2026-50522 Under Active Exploitation After Public PoC

The Hacker News · 21 Jul 2026

A third SharePoint Server flaw patched by Microsoft as part of its Patch Tuesday update for July 2026 has come under active exploitation, per watchTowr. The vulnerability in question is CVE-2026-50522 (CVSS score: 9.8), a critical deserialization of untrusted data in Microsoft Office SharePoint that could allow an unauthorized attacker to execute code over a network. Microsoft credited DEVCORE

Recent mention · Daily CyberSecurity

CVE-2026-50522 SharePoint RCE Flaw Exploited in the Wild With Public PoC Exploit

Daily CyberSecurity · 21 Jul 2026

TL;DR CVE-2026-50522 is a critical SharePoint RCE flaw rated CVSS 9.8. Researchers report active exploitation attempts, and a The post CVE-2026-50522 SharePoint RCE Flaw Exploited in the Wild With Public PoC Exploit appeared first on Daily CyberSecurity.

Recent mention · Rapid7

CVE-2026-58644: Microsoft SharePoint Server Unauthenticated Remote Code Execution Vulnerability Exploited in the Wild

Rapid7 · 17 Jul 2026

OverviewOn July 14, 2026, Microsoft published a security advisory addressing CVE-2026-58644, a critical remote code execution (RCE) vulnerability affecting on-premises Microsoft SharePoint Server deployments. The vulnerability, which carries a CVSS v3.1 score of 9.8 (Critical), results from the deserialization of untrusted data (CWE-502) and allows an unauthenticated attacker to execute arbitrary code.Microsoft confirmed active exploitation of CVE-2026-58644, and the vulnerability was subsequently added to CISA’s Known Exploited Vulnerabilities (KEV) catalog on July 16, 2026. In parallel,...

Recent mention · Zero Day Initiative Published Advisories

ZDI-26-412: (Pwn2Own) Microsoft SharePoint Deserialization of Untrusted Data Remote Code Execution Vulnerability

Zero Day Initiative Published Advisories · 15 Jul 2026

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Microsoft SharePoint. Authentication is not required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 8.1. The following CVEs are assigned: CVE-2026-50522.

Recent mention · Zero Day Initiative Published Advisories

ZDI-26-413: (Pwn2Own) Microsoft SharePoint Improper Verification of Cryptographic Signature Remote Code Execution Vulnerability

Zero Day Initiative Published Advisories · 15 Jul 2026

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Microsoft SharePoint. Authentication is not required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 8.1. The following CVEs are assigned: CVE-2026-50522.

Recent mention · Rapid7

Patch Tuesday - July 2026

Rapid7 · 14 Jul 2026

Microsoft is publishing 622 vulnerabilities on July 2026 Patch Tuesday, including a record-breaking 416 Windows vulnerabilities. Microsoft is aware of exploitation in the wild for two of the vulnerabilities published today, both of which are listed on CISA KEV, as well as public disclosure for one other. As usual, browser vulns are not included in the Patch Tuesday count above. Rapid7 noted last month that Microsoft no longer enumerates Chromium CVEs in the Security Update Guide. However, Microsoft has now taken the pursuit of minimalism much further, since today’s Security Update Guide no...

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

SharePoint SE p2o PoC.ps1

public · Created 2026-07-20 19:29:00 UTC

Timeline

From disclosure to observed exploitation

  1. 00:00 UTC

    KEV confirmed by The Shadowserver

    Exploitation attested by an external source

  2. 03:19 UTC

    Indicators of compromise added (2)

    Indicators of compromise recorded

  3. 03:19 UTC

    Observed by Previdian sensors

    Evidence-backed exploitation signal

  4. 09:13 UTC

    KEV confirmed by CERT-EU

    Exploitation attested by an external source

  5. 21:02 UTC

    KEV confirmed by CVE

    Exploitation attested by an external source

  6. 19:00 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  7. 12:00 UTC

    KEV confirmed by All CISA Advisories

    Exploitation attested by an external source

  8. 20:06 UTC

    KEV confirmed by BleepingComputer

    Exploitation attested by an external source

  9. 15:34 UTC

    KEV confirmed by DarkWebInformer

    Exploitation attested by an external source

  10. 14:57 UTC

    KEV confirmed by The Hacker News

    Exploitation attested by an external source

  11. 12:45 UTC

    KEV confirmed by Daily CyberSecurity

    Exploitation attested by an external source

  12. 10:24 UTC

    KEV confirmed by watchTowr

    Exploitation attested by an external source

  13. 19:29 UTC

    Public PoC available

    Public proof-of-concept code published

  14. 18:18 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  15. 17:05 UTC

    CVE published

    Vulnerability disclosed publicly

  16. 19:00 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

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Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
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GET /api/v2/pro/kevs/CVE-2026-50522

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2026-50522",
  "confidence": "Confirmed",
  "cvss_score": 9.8,
  "cvss_estimated": false,
  "epss_score": 0.03042,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 7, "sensors": 1 }
}