Exploited vulnerability · CISA KEV

Is CVE-2026-45659 exploited? Yes: in CISA KEV since 1 Jul 2026

Gociux · Microsoft SharePoint Server · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2026-45659, Microsoft SharePoint Server Deserialization of Untrusted Data Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 1 Jul 2026, 40 days after it was published. It is known to be used in ransomware campaigns. It affects Microsoft SharePoint Server. If you run it, CISA's required action is: 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 it is

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

What to do

1. Check whether you run it. Look for SharePoint Server in your asset inventory, including appliances and cloud images. Stack check lists every exploited Microsoft CVE at once.
2. Apply the fix. 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.
3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 22 May 2026.
4. Get told next time. Email alerts when CISA adds a CVE for Microsoft.

Other exploited CVEs in SharePoint Server

• CVE-2026-56164: Microsoft SharePoint Server Missing Authentication for Critical Function Vulnerability (14 Jul 2026)
• CVE-2026-32201: Microsoft SharePoint Server Improper Input Validation Vulnerability (14 Apr 2026)
• CVE-2023-24955: Microsoft SharePoint Server Code Injection Vulnerability (26 Mar 2024)
• CVE-2023-29357: Microsoft SharePoint Server Privilege Escalation Vulnerability (10 Jan 2024)

References

• msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659
• nvd.nist.gov/vuln/detail/CVE-2026-45659

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in July 2026 · Microsoft scorecard · act-now radar.