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CVE-2026-45659

Microsoft SharePoint Remote Code Execution Vulnerability

HIGH
8.8
CVSS Score
Published: May 22, 2026 at 10:04 PM UTC
Updated: July 23, 2026 at 07:32 PM UTC
4 products affected across 1 vendorSharePoint ServerSharePoint Server 2019SharePoint Enterprise Server 2016

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Severity
HIGH8.8
Exploitation
CISA KEV
Exploit prediction
EPSS 80%
SSVC
Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score80.2%

EPSS (Exploit Prediction Scoring System) estimates a 80.2% chance this CVE is exploited in the wild within the next 30 days — higher than 100% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

Microsoft SharePoint Server contains a deserialization of untrusted data vulnerability which allows an authorized attacker to execute code over a network.

Required Action
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Ransomware Use
Known
Added to KEV
Jul 1, 2026
Remediation Due
Jul 4, 2026
119 days overdue
Notes
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659
BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
https://nvd.nist.gov/vuln/detail/CVE-2026-45659

Description

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

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

SharePoint Server· Microsoft
95%
v < 16.0.19725.2028016.0.0 ≤ v < 16.0.19725.2028020162019
Affected range stops below 16.0.19725.20280, so it looks safe — our inference, not a vendor statement
SharePoint Enterprise Server 2016· Microsoft
60%
16.0.0 ≤ v < 16.0.5552.100216.0.0
Affected range stops below 16.0.5552.1002, so it looks safe — our inference, not a vendor statement
SharePoint Server 2019· Microsoft
60%
16.0.0 ≤ v < 16.0.10417.2012816.0.0
Affected range stops below 16.0.10417.20128, so it looks safe — our inference, not a vendor statement
SharePoint Server Subscription Edition· Microsoft
60%
16.0.0 ≤ v < 16.0.19725.2028016.0.0
Affected range stops below 16.0.19725.20280, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

Vendor AdvisoryPatch
Source: cverecord
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659
US Government Resource
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-45659

SSVC — Action Prioritization

SSVCActiveNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.8HIGHmicrosoft
Vector?

Quick Info

StatusANALYZED
CWE
CWE-502

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