Detect SmarterMail Missing Authentication for Critical Function (CVE-2026-24423) in Elastic Security
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
Elastic Detection Query
sequence by source.ip with maxspan=5m
[network where event.dataset == "iis.access" and
url.path : ("*/api/*", "*/admin/*", "*/settings/*", "*/interface/*") and
http.request.method : ("POST", "PUT", "DELETE", "PATCH") and
(not exists(user.name) or user.name == "-" or user.name == "") and
http.response.status_code in (200, 201, 204, 302)]
[network where event.dataset == "iis.access" and
url.path : ("*/admin/*", "*/settings/*") and
http.response.status_code in (200, 201)]EQL sequence rule detecting unauthenticated access patterns to SmarterMail critical endpoints. Correlates multiple unauthenticated successful requests from the same IP within a 5-minute window.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate automated backup or migration tools accessing SmarterMail APIs without session-based auth
- Third-party integrations using non-standard authentication mechanisms not captured in IIS logs
- Security scanners performing authenticated testing where credentials appear absent in log fields
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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