Detect Microsoft SharePoint Server Improper Input Validation (CVE-2026-32201) in Splunk
Detects exploitation of CVE-2026-32201, an improper input validation vulnerability in Microsoft SharePoint Server. This vulnerability is actively exploited in the wild (CISA KEV) and allows attackers to send crafted HTTP requests to SharePoint endpoints to bypass input validation controls, potentially enabling unauthorized access, remote code execution, or data exfiltration. CWE-20 class vulnerabilities in SharePoint have historically been leveraged for initial access and lateral movement in enterprise environments.
MITRE ATT&CK
SPL Detection Query
index=iis OR index=sharepoint sourcetype=iis OR sourcetype=ms:sharepoint:audit
| where (uri_path IN ("/_layouts/", "/_api/", "/sites/", "/_vti_bin/") OR match(uri_path, "(?i)/_layouts|/_api|/_vti_bin|/sites/"))
| eval is_suspicious=if(
(method IN ("POST", "PUT", "PATCH") AND (match(uri_query, "(?i)(\.\./|%2e%2e|%00|<script|javascript:)")))
OR (status >= 500)
OR match(uri_path, "(?i)(%2e%2e|;.*\.aspx|/\.\./)"), 1, 0)
| stats count AS total_requests, dc(uri_path) AS unique_paths, values(status) AS status_codes, values(method) AS methods, sum(is_suspicious) AS suspicious_count BY src_ip, span(1m, _time)
| where total_requests > 30 OR suspicious_count > 5
| eval risk_score=case(suspicious_count > 10, "critical", suspicious_count > 5, "high", total_requests > 100, "medium", true(), "low")
| table _time, src_ip, total_requests, unique_paths, suspicious_count, status_codes, methods, risk_score
| sort -suspicious_countDetects SharePoint exploitation patterns for CVE-2026-32201 by analyzing IIS logs for anomalous request volumes, encoded path traversal, and input validation bypass attempts from individual source IPs.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Legitimate SharePoint backup or migration tools generating high request volumes
- Security scanning products configured to test SharePoint endpoints
- SharePoint workflow automation generating repeated API calls
- CDN or proxy services masking multiple users behind a single IP
Other platforms for CVE-2026-32201
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1SharePoint Encoded Path Traversal Probe (CVE-2026-32201)
Expected signal: IIS W3C log entry with cs-uri-stem=/_layouts/15/start.aspx, cs-uri-query containing %2e%2e%2f, cs-method=POST, and HTTP status 400 or 500 (or 200 if vulnerable). Network connection event from test host to SharePoint server on TCP/80 or TCP/443.
- Test 2SharePoint REST API Null Byte Injection (CVE-2026-32201)
Expected signal: 10 IIS log entries to /_api/web/lists with POST method, JSON content-type, and null byte (%00) in request body. Windows Security Event 4688 should NOT appear unless RCE achieved. HTTP 400/401/403/500 expected in non-vulnerable or patched environments.
- Test 3SharePoint Webshell Drop via Exploited Upload Endpoint (CVE-2026-32201 Post-Exploitation Simulation)
Expected signal: Windows Security Event 4663 (File System Audit) for new .aspx file creation in SharePoint _layouts directory by process other than normal SharePoint setup. Sysmon Event ID 11 (FileCreate) with TargetFilename matching *.aspx in SharePoint web root paths. IIS log entry for GET request to /_layouts/15/detection_test_cve_2026_32201.aspx returning HTTP 200.
- Test 4High-Volume SharePoint Endpoint Fuzzing (CVE-2026-32201 Scanner Simulation)
Expected signal: 32+ IIS log entries across 4 SharePoint endpoints within ~7 seconds from single source IP. Encoded traversal sequences visible in cs-uri-query fields. Mix of HTTP 400, 403, 404, and 500 response codes expected.
Unlock Pro Content
Get the full detection package for CVE-2026-32201 including response playbook, investigation guide, and atomic red team tests.