Detect SmarterMail Missing Authentication for Critical Function (CVE-2026-24423) in Sumo Logic CSE
Detects exploitation of CVE-2026-24423, a missing authentication vulnerability (CWE-306) in SmarterTools SmarterMail. This KEV-listed vulnerability allows unauthenticated attackers to access critical functions in SmarterMail, potentially enabling unauthorized administrative access, data exfiltration, or further lateral movement. Detection focuses on unauthenticated access patterns to administrative and critical API endpoints.
MITRE ATT&CK
Sumo Detection Query
_sourceCategory=iis OR _sourceCategory=webserver
| parse "* * * * * * * * *" as date, time, s_sitename, s_computername, s_ip, cs_method, cs_uri_stem, cs_uri_query, s_port
| parse "* * * * * *" as cs_username, c_ip, cs_useragent, cs_referer, sc_status, sc_bytes
| where cs_uri_stem matches "*/api/*" or cs_uri_stem matches "*/admin/*" or cs_uri_stem matches "*/settings/*" or cs_uri_stem matches "*/interface/*"
| where cs_method in ("POST", "PUT", "DELETE", "PATCH")
| where isNull(cs_username) or cs_username = "-" or cs_username = ""
| where sc_status in ("200", "201", "204", "302")
| timeslice 5m
| count by c_ip, cs_uri_stem, cs_method, sc_status, _timeslice
| where _count > 1
| sort by _count descSumo Logic query for detecting unauthenticated SmarterMail critical endpoint access via IIS web server logs, aggregated over 5-minute windows to identify exploitation attempts.
Data Sources
Required Tables
False Positives & Tuning
- Monitoring agents or uptime checkers sending health probe requests to SmarterMail without authentication
- SmarterMail internal scheduled tasks that generate IIS log entries appearing as unauthenticated
- Browser preflight CORS requests that may appear unauthenticated before the authenticated request follows
Other platforms for CVE-2026-24423
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 1Unauthenticated GET to SmarterMail Admin API Endpoint
Expected signal: IIS access log entry with csUsername='-', cs-method=GET, sc-status=200, cs-uri-stem=/api/v1/settings/sysadmin/general
- Test 2Unauthenticated POST to SmarterMail User Creation Endpoint
Expected signal: IIS log: csMethod=POST, csUriStem=/api/v1/settings/sysadmin/users, csUsername=-, scStatus=200 or 201. SmarterMail app log: new user creation event for [email protected]
- Test 3Unauthenticated SmarterMail Mail Forwarding Rule Injection
Expected signal: IIS log entry: POST to /api/v1/settings/sysadmin/users/[email protected]/forwardingRules with csUsername='-' and scStatus=200. SmarterMail audit log: forwarding rule added for [email protected] pointing to external domain.
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