Detect CVE-2026-45659 Microsoft SharePoint Server Deserialization RCE in IBM QRadar
Detects exploitation of CVE-2026-45659, a critical deserialization of untrusted data vulnerability in Microsoft SharePoint Server. Successful exploitation allows remote code execution by sending crafted serialized .NET objects to SharePoint web endpoints. This CVE is listed in CISA KEV indicating active exploitation in the wild.
MITRE ATT&CK
- Tactic
- Initial Access Execution Persistence
QRadar Detection Query
SELECT
DATEFORMAT(starttime, 'yyyy-MM-dd HH:mm:ss') AS event_time,
sourceip,
destinationip,
destinationport,
URL,
username,
"BytesSent",
"Application",
QIDNAME(qid) AS event_name,
logsourcename(logsourceid) AS log_source
FROM events
WHERE
LAST 24 HOURS
AND (
(
logsourcetypename(devicetype) ILIKE '%IIS%'
AND URL ILIKE ANY ('%_vti_bin%', '%_layouts%', '%viewlsts.aspx%', '%_api/%', '%upload.aspx%')
AND "HTTPMethod" IN ('POST', 'PUT')
AND CAST("BytesSent" AS BIGINT) > 5000
)
OR
(
logsourcetypename(devicetype) ILIKE '%Windows%'
AND "ParentProcessPath" ILIKE ANY ('%w3wp.exe%', '%owstimer.exe%')
AND "ProcessPath" ILIKE ANY ('%cmd.exe%', '%powershell.exe%', '%wscript.exe%', '%cscript.exe%', '%mshta.exe%', '%rundll32.exe%')
)
)
ORDER BY starttime DESCQRadar AQL query detecting CVE-2026-45659 SharePoint deserialization exploitation through IIS log anomalies and Windows process creation events showing suspicious child processes from SharePoint worker processes.
Data Sources
Required Tables
False Positives & Tuning
- SharePoint farm administrators running PowerShell scripts that upload content via the web front-end
- Legitimate content management or migration operations using large payloads against SharePoint APIs
- Scheduled SharePoint timer jobs (owstimer.exe) that legitimately spawn child processes for maintenance tasks
Other platforms for CVE-2026-45659
Testing Methodology
Validate this detection against 3 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 1CVE-2026-45659 SharePoint Deserialization Simulation via ysoserial.net
Expected signal: IIS logs should show POST request to /_vti_bin/UserProfileService.asmx with large cs-bytes; Sysmon Event ID 1 should capture cmd.exe spawned by w3wp.exe with CommandLine containing whoami
- Test 2SharePoint Worker Process Suspicious Child Simulation
Expected signal: Sysmon Event ID 1 showing cmd.exe execution with Network Service account; Windows Security Event ID 4688 capturing process creation with suspicious command line arguments
- Test 3SharePoint Endpoint Fuzzing and Web Shell Upload Detection Test
Expected signal: Sysmon Event ID 11 (FileCreate) capturing .aspx file creation in SharePoint web directory path; Windows Security Event ID 4663 (file access) if object access auditing is enabled
References (4)
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
- https://nvd.nist.gov/vuln/detail/CVE-2026-45659
Unlock Pro Content
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