Microsoft SharePoint Server Missing Authentication for Critical Function Vulnerability
CVE-2026-56164 is a security vulnerability in Microsoft SharePoint Server, added to CISA KEV on July 14, 2026. Patch order: fourth of four.
What is CVE-2026-56164?
Microsoft SharePoint contains a missing authentication for critical function vulnerability that allows an unauthorized attacker to elevate privileges over a network.
Who is affected by CVE-2026-56164?
Affects anyone running Microsoft SharePoint Server. Microsoft products in a small practice typically sit close to credentials, email, or document workflows — treat the patch as in-scope.
What should I do about CVE-2026-56164?
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.
If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Request a free review.
Insurance readiness
Your insurer will ask if this is patched.
Unpatched entries on CISA's Known Exploited Vulnerabilities list are exactly what cyber-insurance carrier questionnaires probe for, and knowing which controls they check is how you keep a renewal from stalling.
Get the free carrier questionnaire →Severity
CVSS base score: 5.3 — MEDIUM
Weakness classification: CWE-306
Microsoft fix
Microsoft Exploitability Index (assessed at update release): Exploitation Detected
Microsoft has confirmed in-the-wild exploitation in the latest software release. This aligns with CISA's listing of this CVE.
Vendor workaround
Vendor-published mitigation
The following mitigating factors might be helpful in your situation:
Enable AMSI: Ensure the Antimalware Scan Interface (AMSI) is actively integrated and scanning SharePoint and IIS worker process memory. Enable AMSI scan feature and set the Request Body Scan mode to Full in order for POST body payloads to be detected.
Configure AMSI integration with SharePoint Server - https://learn.microsoft.com/en-us/sharepoint/security-for-sharepoint-server/configure-amsi-integration
A workaround reduces exposure while you patch — it is not a substitute for the update. Install the fix above as soon as you can.
CISA due date
CISA's listed due date: July 17, 2026.
Federal civilian agencies work under CISA's Binding Operational Directive 26-04, which replaced BOD 22-01 on June 10, 2026. It sets the deadline for each affected system by:
- How exposed that system is to the internet
- Whether the attack can be automated
- How much control it gives an attacker
Its table gives catalogued vulnerabilities 3 or 14 days.
None of this binds a private business, but treat the date as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
EPSS
EPSS score: 1.0% — higher than 62% of all scored CVEs.
EPSS estimates the probability of exploitation activity in the next 30 days. Every entry on this site is already confirmed exploited, so read it as relative urgency among the things you still have open, not as permission to wait.
Other exploited Microsoft SharePoint Server entries
More CISA KEV entries for Microsoft SharePoint Server. Same product line, same actively-exploited status.
Source
This entry comes from CISA's Known Exploited Vulnerabilities catalog, public US-Government data we pull daily. The plain-language framing and the what-to-do guidance above are ours. View the original entry on cisa.gov.