CVE-2025-52691 CrowdStrike LogScale · LogScale

Detect SmarterMail Unrestricted File Upload Exploitation (CVE-2025-52691) in CrowdStrike LogScale

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

LogScale Detection Query

CrowdStrike LogScale (LogScale)
cql 
event_simpleName IN ("FileCreate", "ProcessRollup2")
| eval lower_path=lower(TargetFileName), lower_image=lower(ImageFileName), lower_parent=lower(ParentBaseFileName)
| where (
    (event_simpleName="FileCreate"
      AND (lower_path LIKE "%smartermail%" OR lower_path LIKE "%mailroot%" OR lower_path LIKE "%webmail%")
      AND match(lower_path, @"\.(aspx|asp|php|jsp|cfm|cgi|pl|exe|dll|bat|cmd|ps1|vbs|hta)$"))
    OR
    (event_simpleName="ProcessRollup2"
      AND lower_parent LIKE "%smartermail.exe%"
      AND (lower_image LIKE "%cmd.exe%" OR lower_image LIKE "%powershell.exe%" OR lower_image LIKE "%wscript.exe%"
           OR lower_image LIKE "%cscript.exe%" OR lower_image LIKE "%mshta.exe%" OR lower_image LIKE "%certutil.exe%"))
  )
| table _time, ComputerName, UserName, event_simpleName, TargetFileName, ImageFileName, ParentBaseFileName, CommandLine
| sort -_time
critical severity high confidence

CrowdStrike Falcon Query Language detection for file creation with dangerous extensions in SmarterMail directories and suspicious child process execution from SmarterMail parent, indicating active exploitation of CVE-2025-52691.

Data Sources

CrowdStrike Falcon EDRCrowdStrike Event Stream

Required Tables

event_simpleName=FileCreateevent_simpleName=ProcessRollup2

False Positives & Tuning

  • CrowdStrike sensor or other security agent processes spawning from SmarterMail service context
  • Legitimate automated deployment pipelines writing configuration files with unusual extensions to mail server paths
  • SmarterMail licensed add-ons or third-party integrations that create executable content in the application directory

Other platforms for CVE-2025-52691

Microsoft Sentinel (KQL) Splunk (SPL) Elastic Security (Elastic) IBM QRadar (QRadar) Sumo Logic CSE (Sumo) Google Chronicle (YARA-L) All platforms (combined) →

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.

  1. 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

  2. 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'

  3. 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

  4. 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

Last updated: 2026-06-19 Research depth: standard
References (3)

Response Playbook

Triage

  1. Identify the SmarterMail server(s) affected by reviewing file creation alerts for dangerous extensions (ASPX, PHP, JSP, etc.) under the SmarterMail web root and mail directories.
  2. Determine the source IP address of the HTTP/S request that triggered the file upload by correlating IIS or SmarterMail access logs with the timestamp of the suspicious file creation event.
  3. Check whether the uploaded file has been accessed or executed subsequent to creation by reviewing web server access logs for requests to the file path and process creation events with the uploaded file as initiator.
  4. Assess the scope of compromise by searching for lateral movement indicators, additional web shells, or persistence mechanisms (scheduled tasks, registry run keys, new service installs) on the affected host.

Containment

  1. Immediately isolate the SmarterMail server from the network or restrict inbound web access (ports 80/443/8080/9998) via firewall rule to prevent further exploitation or attacker interaction with any uploaded web shell.
  2. Delete or quarantine any identified uploaded files with dangerous extensions from the SmarterMail web directory, and reset credentials for all accounts with access to the SmarterMail administration interface.

Evidence Collection

  1. Collect IIS or SmarterMail web server access logs covering the period around the file creation event, preserving the full HTTP request headers, body size, and source IP for forensic analysis.
  2. Capture a memory image and disk forensic image of the affected SmarterMail server before remediation to preserve volatile evidence of attacker activity and any in-memory web shell or implant.

Escalation Criteria

  • !Escalate immediately to incident response if the uploaded file has been accessed or executed, indicating active post-exploitation, or if evidence of lateral movement from the mail server to other internal systems is detected.
  • !Escalate to senior security leadership and legal/compliance if email data exfiltration is suspected, given that SmarterMail hosts sensitive communications and PII that may trigger breach notification obligations.

Investigation Guide

Related Techniques

[object Object][object Object][object Object]

Forensic Artifacts

  • >SmarterMail web server access logs (IIS logs at %SystemDrive%\inetpub\logs\LogFiles or SmarterMail-specific logs at %ProgramData%\SmarterTools\SmarterMail\Logs) containing HTTP POST requests to upload endpoints
  • >File system artifacts: newly created files with dangerous extensions (ASPX, PHP, JSP, etc.) in the SmarterMail installation directory (typically C:\Program Files (x86)\SmarterTools\SmarterMail\MRS\)
  • >Windows Security Event Log (Event ID 4688) and Sysmon logs (Event ID 1, 11) showing child process creation from SmarterMail.exe and file creation events in mail server directories
  • >Network flow records showing inbound HTTP/S connections to the SmarterMail server's web interface ports (80, 443, 9998) from external IP addresses at the time of exploitation

Tuning Guidance

Tune the detection by first establishing a baseline of legitimate file types created in SmarterMail directories during normal operations (updates, plugin installs). Whitelist known-good SmarterMail update processes by their hash or signed certificate. For the child process detection, create exclusions for specific monitoring tools (antivirus, backup agents) known to be invoked from service accounts associated with SmarterMail. Adjust the file extension list based on the specific SmarterMail version's web technology stack — older versions using Classic ASP may generate more ASP extension noise during legitimate operations.

Hunting Queries

Hunt for low-frequency file creation events with dangerous extensions in SmarterMail directories over the past 30 days to identify historically uploaded web shells or malicious files that may have evaded real-time detection.

Hunting — KQL
kql 
DeviceFileEvents
| where TimeGenerated > ago(30d)
| where InitiatingProcessName =~ "SmarterMail.exe" or FolderPath contains "SmarterMail"
| where FileName matches regex @"(?i)\.(aspx|asp|php|jsp|cfm|cgi|pl|exe|dll|bat|cmd|ps1|vbs|hta)$"
| summarize FileCount=count(), FirstSeen=min(TimeGenerated), LastSeen=max(TimeGenerated) by DeviceName, FileName, FolderPath, InitiatingProcessName
| where FileCount < 5
| order by LastSeen desc
Hunting — SPL
spl 
index=sysmon EventCode=11
| eval lower_path=lower(TargetFilename)
| where (lower_path LIKE "%smartermail%" OR lower_path LIKE "%mailroot%")
  AND match(lower_path, "\.(aspx|asp|php|jsp|exe|dll|bat|cmd|ps1|vbs|hta)$")
| bin _time span=1d
| stats count AS DailyCount values(TargetFilename) AS Files by _time, host
| where DailyCount < 10
| sort -_time

Atomic Red Team Tests

Test 1 Simulate Web Shell Upload to SmarterMail Directory
windows

Simulates an attacker uploading a web shell file with an ASPX extension to a directory mimicking the SmarterMail web root, triggering file creation telemetry without executing malicious code.

Command

powershell 
New-Item -Path 'C:\Temp\SmarterMail\MRS\shell_test.aspx' -ItemType File -Force -Value '<%@ Page Language="C#" %><% Response.Write("test"); %>'

Cleanup

powershell 
Remove-Item -Path 'C:\Temp\SmarterMail\MRS\shell_test.aspx' -Force -ErrorAction SilentlyContinue; Remove-Item -Path 'C:\Temp\SmarterMail' -Recurse -Force -ErrorAction SilentlyContinue

Expected Telemetry

Sysmon Event ID 11 (FileCreate) with TargetFilename containing 'SmarterMail' and ending in '.aspx'; DeviceFileEvents in Defender with ActionType=FileCreated

Expected Detection

Rule should trigger on file creation of .aspx extension within a path matching 'smartermail' pattern

Test 2 Simulate SmarterMail Spawning Suspicious Child Process
windows

Simulates post-exploitation activity where a web shell executed under SmarterMail context spawns cmd.exe, mimicking command execution after successful file upload exploitation.

Command

powershell 
Start-Process -FilePath 'cmd.exe' -ArgumentList '/c whoami > C:\Temp\smartermail_test_output.txt' -Wait

Cleanup

powershell 
Remove-Item -Path 'C:\Temp\smartermail_test_output.txt' -Force -ErrorAction SilentlyContinue

Expected Telemetry

Sysmon Event ID 1 (ProcessCreate) showing cmd.exe with parent process context; DeviceProcessEvents showing cmd.exe creation with CommandLine containing 'whoami'

Expected Detection

Process creation rule should flag cmd.exe spawning — in production this would be correlated with SmarterMail.exe as parent; adjust test to use a renamed SmarterMail stub if full simulation is needed

Test 3 Upload Executable File to Simulated Mail Server Web Directory
windows

Tests detection of executable file creation in a SmarterMail-like directory path, simulating an attacker uploading a binary payload alongside or instead of a web shell.

Command

powershell 
New-Item -Path 'C:\Temp\mailroot\webmail\' -ItemType Directory -Force; Copy-Item -Path 'C:\Windows\System32\calc.exe' -Destination 'C:\Temp\mailroot\webmail\update.exe' -Force

Cleanup

powershell 
Remove-Item -Path 'C:\Temp\mailroot' -Recurse -Force -ErrorAction SilentlyContinue

Expected Telemetry

Sysmon Event ID 11 (FileCreate) with TargetFilename matching 'C:\Temp\mailroot\webmail\update.exe'; file hash telemetry for the copied executable

Expected Detection

Rule should trigger on .exe creation within a path matching 'mailroot' or 'webmail' pattern, flagging the file as a potentially dangerous upload

Test 4 Simulate PowerShell Execution via Web Shell Context
windows

Simulates an attacker using an uploaded web shell to execute PowerShell for reconnaissance, a common post-exploitation step following successful CVE-2025-52691 exploitation.

Command

powershell 
powershell.exe -NoProfile -NonInteractive -Command "Get-LocalUser | Select-Object Name,Enabled | ConvertTo-Json" > C:\Temp\recon_output.txt

Cleanup

powershell 
Remove-Item -Path 'C:\Temp\recon_output.txt' -Force -ErrorAction SilentlyContinue

Expected Telemetry

Sysmon Event ID 1 (ProcessCreate) for powershell.exe with CommandLine containing reconnaissance commands; PowerShell Script Block Logging (Event ID 4104) if enabled

Expected Detection

Child process detection rule triggers on powershell.exe execution; in production correlated with SmarterMail.exe parent process indicating web shell execution chain

Related Detections

Tactic Hubs

TA0001Initial AccessTA0002ExecutionTA0003Persistence

Related Techniques

T1190Exploit Public-Facing ApplicationT1505.003Web ShellT1059Command and Scripting Interpreter

Same Tactic: Initial Access

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