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Vulnerabilities

Vulnerability · CVE-2026-45659

Microsoft SharePoint Server Deserialization of Untrusted Data Vulnerability

Published May 22, 2026 · catalog updated Jul 23, 2026 · sharepoint server

Patch now

CVE-2026-45659 is in the CISA known-exploited catalog, due Jul 4, 2026. Confirm sharepoint server against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
High8.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
2.70%
Remediation
Remediation guidance
Affected products
cpe microsoft/sharepoint server · vendor Microsoft SharePoint · vendor Microsoft SharePoint Server

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

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe microsoft/sharepoint server2016
  • cpe microsoft/sharepoint server2019
  • vendor Microsoft SharePointversion unspecified
  • vendor Microsoft SharePoint Serverversion unspecified

How to fix CVE-2026-45659

  • Recommended remediation

    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. CISA due date Jul 4, 2026.

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2026-45659 is in the CISA known-exploited catalog, due Jul 4, 2026. Confirm sharepoint server against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with microsoft/sharepoint server 2016; microsoft/sharepoint server 2019. 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.

What should an analyst verify?

CWE-502: Deserialization of Untrusted Data. EPSS 2.70%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 22, 2026 · Catalog

    Detected

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

  2. Jul 1, 2026 · CISA KEV

    Known exploited

    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

  3. Jul 4, 2026 · CISA KEV

    Remediation due

    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

  4. Jul 23, 2026 · Catalog

    Updated

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

  5. Jul 23, 2026 · NIST NVD

    Updated

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

Sources

  • CISA KEVConfirmed exploitationCVE-2026-45659

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

    cisa.gov
  • CVE.orgVulnerability recordCVE-2026-45659

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-45659

    30-day exploitation probability 2.7%

    first.org
  • NIST NVDVulnerability recordCVE-2026-45659

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

    nvd.nist.gov
  • VulnCheck KEVConfirmed exploitationCVE-2026-45659

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

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.