CVE-2019-25364
📋 TL;DR
MailCarrier 2.51 contains a critical buffer overflow vulnerability in its POP3 service that allows remote attackers to execute arbitrary code by sending an oversized USER command. This affects all systems running MailCarrier 2.51 with POP3 enabled, potentially giving attackers complete control over vulnerable servers.
💻 Affected Systems
- MailCarrier
📦 What is this software?
Mailcarrier by Tabslab
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to full system compromise, data theft, ransomware deployment, and persistent backdoor installation.
Likely Case
Remote code execution resulting in system takeover, credential harvesting, and lateral movement within the network.
If Mitigated
Denial of service if exploit fails, but successful exploitation typically leads to complete compromise.
🎯 Exploit Status
Public exploit code exists on Exploit-DB (ID 47554). Attack requires no authentication and is straightforward to execute.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown - MailCarrier appears to be abandoned software
Vendor Advisory: https://www.tabslab.com/
Restart Required: No
Instructions:
No official patch available. Consider migrating to supported mail server software.
🔧 Temporary Workarounds
Disable POP3 Service
windowsCompletely disable the POP3 service in MailCarrier configuration
Navigate to MailCarrier configuration and disable POP3 service
Network Segmentation
allBlock POP3 port (110) at network perimeter and restrict internal access
firewall rule: block TCP port 110 inbound and outbound
🧯 If You Can't Patch
- Migrate to supported mail server software immediately
- Implement strict network segmentation and isolate MailCarrier servers
🔍 How to Verify
Check if Vulnerable:
Check MailCarrier version in application interface or registry: HKEY_LOCAL_MACHINE\SOFTWARE\MailCarrier\VersionCheck Version:
reg query "HKLM\SOFTWARE\MailCarrier" /v VersionVerify Fix Applied:
Verify POP3 service is disabled or port 110 is blocked and inaccessible📡 Detection & Monitoring
Log Indicators:
- Unusually long USER commands in POP3 logs
- Multiple failed POP3 connections with oversized buffers
Network Indicators:
- Large payloads sent to TCP port 110
- Exploit pattern matching from public exploit code
SIEM Query:
source_port=110 AND (payload_size>1000 OR contains(payload, 'USER ') AND length(payload)>200)