Detect SmarterMail Authentication Bypass via Alternate Path or Channel (CVE-2026-23760) in Sumo Logic CSE
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
Sumo Detection Query
_sourceCategory=iis* OR _sourceCategory=webserver*
| parse regex "(?<src_ip>\d+\.\d+\.\d+\.\d+)\s+\S+\s+\S+\s+\[(?<timestamp>[^\]]+)\]\s+\"(?<method>\w+)\s+(?<uri_path>[^\s\?]+)(?:\?(?<uri_query>[^\s\"]*))?\s+HTTP[^\"]*\"\s+(?<status>\d+)"
| where uri_path matches "*/api/*" or uri_path matches "*/autodiscover/*" or uri_path matches "*/ews/*" or uri_path matches "*/admin*" or uri_path matches "*/config*"
| where method in ("POST","GET","PUT")
| where status in ("200","201","302")
| where (uri_query matches "*bypass*" or uri_query matches "*token=*" or uri_query matches "*auth=*")
| timeslice 5m
| stats count as request_count, count_distinct(uri_path) as distinct_paths, values(uri_path) as paths by _timeslice, src_ip
| where request_count > 10 or distinct_paths > 5
| sort by request_count descSumo Logic query to surface high-frequency or parameter-suspicious requests to SmarterMail web endpoints that may indicate authentication bypass exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Automated mail system integrations generating bulk API requests with predictable query patterns
- Security assessment tools probing SmarterMail endpoints during authorized penetration tests
- Shared mail gateway services that aggregate requests from multiple users through a single IP
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'
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