Detect SmarterMail Unrestricted File Upload Exploitation (CVE-2025-52691) in Elastic Security
Detects exploitation of CVE-2025-52691, an unrestricted file upload vulnerability in SmarterTools SmarterMail. This vulnerability allows attackers to upload files with dangerous types (e.g., web shells, executables) to the mail server, potentially enabling remote code execution. This CVE is listed in CISA's Known Exploited Vulnerabilities catalog.
MITRE ATT&CK
- Tactic
- Initial Access Execution Persistence
Elastic Detection Query
sequence by host.name with maxspan=5m
[
network where process.name : "SmarterMail.exe"
and network.direction : "ingress"
and destination.port in (80, 443, 8080, 9998)
] by host.name
[
file where event.action : "creation"
and process.name : "SmarterMail.exe"
and file.extension : ("aspx", "asp", "php", "jsp", "cfm", "cgi", "pl", "exe", "dll", "bat", "cmd", "ps1", "vbs", "hta")
and file.path : ("*smartermail*", "*SmarterMail*", "*mailroot*", "*webmail*")
] by host.nameCorrelates inbound network connections to SmarterMail followed by suspicious file creation with dangerous extensions, indicating a multi-stage file upload exploitation of CVE-2025-52691.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate web-based SmarterMail administration uploading configuration files
- Authorized penetration testing or red team exercises against the mail server
- SmarterMail self-update mechanism downloading and staging new executable files
Other platforms for CVE-2025-52691
Testing Methodology
Validate this detection against 4 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 1Simulate Web Shell Upload to SmarterMail Directory
Expected signal: Sysmon Event ID 11 (FileCreate) with TargetFilename containing 'SmarterMail' and ending in '.aspx'; DeviceFileEvents in Defender with ActionType=FileCreated
- Test 2Simulate SmarterMail Spawning Suspicious Child Process
Expected signal: Sysmon Event ID 1 (ProcessCreate) showing cmd.exe with parent process context; DeviceProcessEvents showing cmd.exe creation with CommandLine containing 'whoami'
- Test 3Upload Executable File to Simulated Mail Server Web Directory
Expected signal: Sysmon Event ID 11 (FileCreate) with TargetFilename matching 'C:\Temp\mailroot\webmail\update.exe'; file hash telemetry for the copied executable
- Test 4Simulate PowerShell Execution via Web Shell Context
Expected signal: Sysmon Event ID 1 (ProcessCreate) for powershell.exe with CommandLine containing reconnaissance commands; PowerShell Script Block Logging (Event ID 4104) if enabled
Unlock Pro Content
Get the full detection package for CVE-2025-52691 including response playbook, investigation guide, and atomic red team tests.