CVE-2025-53771 — Sharepoint Server
MEDIUMCVE-2025-53771 is a medium-severity (CVSS 6.5) Improper Authentication vulnerability in microsoft sharepoint server. EPSS puts its 30-day exploitation probability at 99.9% (100th percentile). A fix is available — see the affected versions and patch details below.
Improper authentication in Microsoft Office SharePoint allows an unauthorized attacker to perform spoofing over a network.
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-53771.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2025-53771 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 397,508 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Improper authentication in Microsoft Office SharePoint allows an unauthorized attacker to perform spoofing over a network.
Affected Products
sharepoint servermicrosoftDetection & mitigation playbook
Vendor / applianceDetect
Inventory every microsoft sharepoint server deployment and check each version against the affected-products list above.
Fix
Apply the microsoft sharepoint server security patch or hotfix for CVE-2025-53771 on the affected version, following the vendor advisory for your exact build.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2025-53771
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2025-53771 -u https://target- Template
- Microsoft SharePoint Server - Authentication Bypass (ToolShell)
- Severity
- medium
- Impact
- Unauthenticated attackers can bypass SharePoint authentication controls by spoofing the Referer header, gaining unauthorized access to protected administrative endpoints. When combined with CVE-2025-53770, this leads to full remote code execution and system compromise.
- Remediation
- Apply the latest security patches from Microsoft released on July 21, 2025. Additionally, rotate ASP.NET MachineKey values (ValidationKey and DecryptionKey) on all SharePoint servers using Set-SPMachineKey or Update-SPMachineKey, then restart IIS.
Template by ProjectDiscovery nuclei-templates (_l0gg, SamIntruder, sfewer-r7), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2025-53771 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.