KEV Intelligence

Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2026-45659

Microsoft SharePoint Remote Code Execution Vulnerability

Microsoft / Microsoft SharePoint Enterprise Server 2016 · affected before 16.0.5552.1002

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Severity
CVSS 8.8 · High
Confidence
Confirmed
Exploit status
Exploited in the wild
EPSS
9.9%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2026-45659 is Microsoft SharePoint Remote Code Execution Vulnerability. Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

Is it exploited?

Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.

Who is affected?

Microsoft / Microsoft SharePoint Enterprise Server 2016 affected before 16.0.5552.1002.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Microsoft SharePoint Remote Code Execution Vulnerability

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

Vendor Product Affected Status
Microsoft Microsoft SharePoint Enterprise Server 2016 Before 16.0.5552.1002 Affected
Microsoft Microsoft SharePoint Server 2019 Before 16.0.10417.20128 Affected
Microsoft Microsoft SharePoint Server Subscription Edition Before 16.0.19725.20280 Affected
View vendor advisory (opens in new tab)
Published
22 May 2026
Exploitation Reported
01 Jul 2026
Attack vector
Remote
Complexity
Low
Privileges
Low
User interaction
None

Tags

microsoft cisa

CVE References

Exploitation evidence

Why KEV Intelligence 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

CISA

Recorded 01 Jul 2026

Independent exploitation attestation added to the KEV Intelligence record.

Known exploited vulnerability sources

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

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Source Added
CISA First 2026-07-01 19:00 UTC
CVE 2026-07-01 20:31 UTC
All CISA Advisories 2026-07-01 21:20 UTC
TheHackerNews 2026-07-02 07:21 UTC
Daily CyberSecurity 2026-07-15 01:05 UTC
Tenable Blog 2026-07-16 16:00 UTC
CERT-EU 2026-07-23 09:13 UTC

Detection

Operational artifacts and observed signals

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

Observed signals

Request targets
0
User-Agents
0

Raw values available in Pro and Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

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

Learn about virtual patches →

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

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

EPSS

9.9%

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...

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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 · Tenable Blog

CVE-2026-32201, CVE-2026-45659, CVE-2026-56164: Frequently Asked Questions About Active Exploitation of Microsoft SharePoint Server Vulnerabilities

Tenable Blog · 16 Jul 2026

Four Microsoft SharePoint Server vulnerabilities are under active exploitation, prompting CISA to issue a hardening alert. An additional high-severity flaw recently patched adds pressure for organizations running on-premises deployments.Key TakeawaysCISA confirmed active exploitation of three on-premises SharePoint Server vulnerabilities (CVE-2026-32201, CVE-2026-45659, CVE-2026-56164), used to gain unauthorized access, establish remote code execution, steal IIS machine keys and deploy malware for persistence.Two additional SharePoint Server vulnerabilities disclosed on July 14, 2026,...

Recent mention · Daily CyberSecurity

CISA Warns Three SharePoint Server Vulnerabilities Are Exploited in the Wild, Urges Hardening

Daily CyberSecurity · 15 Jul 2026

TL;DR CISA has confirmed active exploitation of three SharePoint vulnerabilities: CVE-2026-32201, CVE-2026-45659, and CVE-2026-56164. Threat actors chain them The post CISA Warns Three SharePoint Server Vulnerabilities Are Exploited in the Wild, Urges Hardening appeared first on Daily CyberSecurity.

Recent mention · All CISA Advisories

CISA Urges SharePoint Hardening After New Exploitations

All CISA Advisories · 14 Jul 2026

CISA is aware of active exploitation of vulnerabilities CVE-2026-32201, CVE-2026-45659, and CVE-2026-56164, enabling cyber threat actors to gain unauthorized access to on-premises SharePoint Server instances. These vulnerabilities affect all supported on-premises SharePoint Server versions (Subscription Edition, 2019, and 2016) and involve establishing remote code execution (RCE) and post-exploitation activities, such as stealing Internet Information Services (IIS) machine keys and performing deserialization techniques, to gain persistence and deploy malware. Organizations should monitor...

Recent mention · TheHackerNews

SharePoint RCE CVE-2026-45659 Added to CISA KEV After Active Exploitation

TheHackerNews · 02 Jul 2026

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Wednesday added a high-severity flaw impacting Microsoft SharePoint Server to its Known Exploited Vulnerabilities (KEV) catalog, citing evidence of active exploitation. The vulnerability, tracked as CVE-2026-45659 (CVSS score: 8.8), is a case of remote code execution arising from the deserialization of untrusted data. The issue

Recent mention · All CISA Advisories

CISA Adds One Known Exploited Vulnerability to Catalog

All CISA Advisories · 01 Jul 2026

CISA has added one new vulnerability to its Known Exploited Vulnerabilities (KEV) Catalog, based on evidence of active exploitation. CVE-2026-45659 Microsoft SharePoint Server Deserialization of Untrusted Data Vulnerability This type of vulnerability is a frequent attack vector for malicious cyber actors and poses significant risks to the federal enterprise. Binding Operational Directive (BOD) 26-04: Prioritizing Security Updates Based on Risk establishes vulnerability management requirements for Federal Civilian Executive Branch (FCEB) agencies. BOD 26-04 reinforces the importance of the...

Recent mention · TheHackerNews

Microsoft Patches SharePoint RCE Flaw CVE-2026-45659 Across Server Versions

TheHackerNews · 26 May 2026

Microsoft has rolled out updates to fix a remote code execution vulnerability impacting SharePoint that could be exploited by bad actors in attacks without requiring any specialized conditions to be met. The vulnerability, tracked as CVE-2026-45659, carries a CVSS score of 8.8. It has been assigned an important severity. "Deserialization of untrusted data in Microsoft Office SharePoint allows

Timeline

From disclosure to observed exploitation

  1. KEV confirmed by CERT-EU

    Exploitation attested by an external source

  2. KEV confirmed by Tenable Blog

    Exploitation attested by an external source

  3. KEV confirmed by Daily CyberSecurity

    Exploitation attested by an external source

  4. KEV confirmed by TheHackerNews

    Exploitation attested by an external source

  5. KEV confirmed by All CISA Advisories

    Exploitation attested by an external source

  6. KEV confirmed by CVE

    Exploitation attested by an external source

  7. Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  8. CVE published

    Vulnerability disclosed publicly

  9. CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

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
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2026-45659

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2026-45659",
  "confidence": "Confirmed",
  "cvss_score": 8.8,
  "epss_score": 0.09863,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

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