Detect SmarterMail Authentication Bypass via Alternate Path or Channel (CVE-2026-23760) in IBM QRadar
Detects exploitation of CVE-2026-23760, an authentication bypass vulnerability (CWE-288) in SmarterTools SmarterMail. Attackers can access protected functionality through an alternate path or channel without valid credentials, potentially leading to unauthorized mailbox access, data exfiltration, or lateral movement. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.
MITRE ATT&CK
- Tactic
- Initial Access Credential Access
QRadar Detection Query
SELECT
sourceip,
DATEFORMAT(starttime, 'yyyy-MM-dd HH:mm:ss') AS event_time,
URL,
"HTTP Method" AS http_method,
"HTTP Response Code" AS response_code,
"User-Agent" AS user_agent,
COUNT(*) AS request_count
FROM events
WHERE
LOGSOURCETYPENAME(devicetype) ILIKE '%IIS%'
AND (
URL ILIKE '%/api/%'
OR URL ILIKE '%/autodiscover/%'
OR URL ILIKE '%/ews/%'
OR URL ILIKE '%/mapi/%'
OR URL ILIKE '%/admin%'
OR URL ILIKE '%/config%'
)
AND "HTTP Method" IN ('POST', 'GET', 'PUT')
AND "HTTP Response Code" IN ('200', '201', '302')
AND (
URL ILIKE '%bypass%'
OR URL ILIKE '%token=%'
OR URL ILIKE '%auth=%'
OR ("User-Agent" NOT ILIKE '%Mozilla%' AND URL ILIKE '%/api/%')
)
AND LOGSOURCENAME(logsourceid) ILIKE '%SmarterMail%'
GROUP BY sourceip, URL, http_method, response_code, user_agent, event_time
HAVING COUNT(*) > 5
LAST 30 MINUTESAQL query for QRadar SIEM to detect suspicious authentication-bypass-indicative requests against SmarterMail IIS endpoints, grouped by source IP and resource path.
Data Sources
Required Tables
False Positives & Tuning
- Scheduled tasks or integration middleware accessing SmarterMail APIs with non-standard user agents
- IT management scripts automating mailbox configuration via API
- Third-party email clients using legacy or custom HTTP client libraries
Other platforms for CVE-2026-23760
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 1Probe SmarterMail Admin API Without Credentials
Expected signal: IIS access log entry showing GET /api/v1/settings/sysadmin/general with HTTP 200 or 302, source IP of test host, user-agent 'python-requests/2.28'
- Test 2Enumerate SmarterMail User Accounts via Bypass Path
Expected signal: IIS logs showing sequential requests to /api/v1/accounts, /autodiscover/autodiscover.xml, /ews/exchange.asmx with non-standard user-agent from a single IP within seconds
- Test 3SmarterMail Authentication Bypass via Token Parameter Injection
Expected signal: Windows Event Log network connection events and IIS access log entries showing GET requests with 'token=', 'auth=', 'session=' query parameters, HTTP responses 200/302/401, user-agent 'TestClient/1.0'
Unlock Pro Content
Get the full detection package for CVE-2026-23760 including response playbook, investigation guide, and atomic red team tests.