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Exploited vulnerability · CISA KEV

Is CVE-2026-20963 exploited? Yes: in CISA KEV since 18 Mar 2026

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

Yes. CVE-2026-20963, Microsoft SharePoint Deserialization of Untrusted Data Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 18 Mar 2026, 64 days after it was published. It affects Microsoft SharePoint. If you run it, CISA's required action is: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

exploitedYesCISA KEV · 18 Mar 2026
ransomwareNot knownno confirmed use
EPSStop 5%very likely to be exploited
severity9.8CVSS 3.1 · critical
US federal due21 Mar 2026BOD 22-01 deadline

What it is

Microsoft SharePoint contains a deserialization of untrusted data vulnerability that allows an unauthorized attacker to execute code over a network.

VendorMicrosoft (391 exploited CVEs in KEV)
ProductSharePoint
VulnerabilityMicrosoft SharePoint Deserialization of Untrusted Data Vulnerability
WeaknessCWE-502
Published13 Jan 2026
Added to KEV18 Mar 2026
Reported by (CNA)microsoft

What to do

  1. Check whether you run it. Look for SharePoint in your asset inventory, including appliances and cloud images. Stack check lists every exploited Microsoft CVE at once.
  2. Apply the fix. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
  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 13 Jan 2026.
  4. Get told next time. Email alerts when CISA adds a CVE for Microsoft.

Other exploited CVEs in SharePoint

References

Questions

Is CVE-2026-20963 being exploited?

Yes. CISA added CVE-2026-20963 to the Known Exploited Vulnerabilities catalog on 18 Mar 2026, which means there is reliable evidence of exploitation in the wild.

Is CVE-2026-20963 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2026-20963?

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Check Microsoft's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected SharePoint and watch it for signs of compromise.

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 March 2026 · Microsoft scorecard · act-now radar.

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