CVE-2025-15559
📋 TL;DR
CVE-2025-15559 is an unauthenticated OS command injection vulnerability in NesterSoft WorkTime server's client generation API. Attackers can execute arbitrary commands with SYSTEM privileges by manipulating the 'guid' parameter, potentially compromising the entire server. All organizations using vulnerable WorkTime server installations are affected.
💻 Affected Systems
- NesterSoft WorkTime Server
📦 What is this software?
Worktime by Nestersoft
Worktime by Nestersoft
⚠️ Risk & Real-World Impact
Worst Case
Complete server takeover with SYSTEM privileges, allowing data theft, destruction, lateral movement, and persistent backdoor installation.
Likely Case
Server compromise leading to data exfiltration, ransomware deployment, or use as a foothold for internal network attacks.
If Mitigated
Limited impact if server is isolated, monitored, and has strict network controls, though exploitation remains possible.
🎯 Exploit Status
Simple HTTP request manipulation required; public advisory includes technical details making exploitation straightforward.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown - check vendor for updates
Vendor Advisory: Unknown - monitor NesterSoft website
Restart Required: No
Instructions:
1. Contact NesterSoft for patch availability 2. Apply vendor-provided update 3. Verify fix by testing exploitation attempts
🔧 Temporary Workarounds
Block Vulnerable API Endpoint
windowsRestrict access to the client generation API endpoint using firewall rules or web application controls
Windows Firewall: New-NetFirewallRule -DisplayName "Block WorkTime API" -Direction Inbound -Protocol TCP -LocalPort [WorkTimePort] -RemoteAddress Any -Action Block
Network Segmentation
allIsolate WorkTime server from internet and restrict internal access to authorized users only
🧯 If You Can't Patch
- Immediately isolate the WorkTime server from all network access except absolutely required connections
- Implement strict monitoring and alerting for any access attempts to the vulnerable API endpoint
🔍 How to Verify
Check if Vulnerable:
Test by sending crafted HTTP request to WorkTime server API endpoint with command injection payload in 'guid' parameterCheck Version:
Check WorkTime server interface or installation directory for version informationVerify Fix Applied:
Attempt exploitation after applying vendor patch or workarounds; successful exploitation should be prevented📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP requests to client generation API with special characters in parameters
- System process creation from WorkTime server process
Network Indicators:
- HTTP requests containing shell metacharacters (;, &, |, $) in 'guid' parameter to WorkTime server
SIEM Query:
source="WorkTime" AND (uri="*/api/client/generate*" AND param="guid" AND value MATCHES "[;&|$`]+")