MikroTik Vulnerabilities: Chimay Blue, CVE-2018-14847, and Lessons

CVE-2018-14847: The Chimay Blue MikroTik Vulnerability

In April 2018, a WikiLeaks release called "Vault 7" exposed a CIA exploit for MikroTik routers. This exploit, later publicly known as Chimay Blue, targets a critical vulnerability in the Winbox protocol that allows unauthenticated remote attackers to read arbitrary files from RouterOS — including the user database.

What Is CVE-2018-14847?

• Type: Authentication bypass / arbitrary file read
• Protocol: Winbox (port 8291)
• Affected versions: RouterOS below 6.42.1 (Long-term), 6.43 (Stable)
• Authentication required: None — fully unauthenticated
• Impact: Attacker reads /flash/rw/store/user.dat — the credential database — exposing all usernames and passwords in plaintext

How the Exploit Works (Technical Overview)

The Winbox protocol has a message-based API. CVE-2018-14847 exploits a flaw in how Winbox message handler ecos.mvc processes certain message types:

1. Attacker sends a specially crafted Winbox message without authenticating.
2. The handler processes it as if the user were already authenticated.
3. The attacker requests the file /flash/rw/store/user.dat.
4. RouterOS returns the file content — which contains all user credentials.

Public proof-of-concept code was released within days of the WikiLeaks disclosure. Tools like Chimay-Blue on GitHub implement the exploit as a Python script.

How to Check If Your Device Is Vulnerable

From the router CLI:

/system routeros print

If the version is below 6.42.1 (for Long-term track) or 6.43 (for Stable track), the device is vulnerable.

From an external tool, attackers use:

python3 chimay-blue.py 192.168.1.1

A vulnerable device returns credential data immediately.

Immediate Remediation — Upgrade RouterOS

This is the only true fix:

/system package update set channel=long-term
/system package update check-for-updates
/system package update install

The device reboots after installation. Verify afterward:

/system routeros print

Additional Mitigations

/ip firewall filter
add chain=input protocol=tcp dst-port=8291 src-address=!192.168.88.0/24 action=drop comment="Block Winbox from WAN"

/ip service set winbox disabled=yes

Then use SSH or WebFig (HTTPS) for management.

Look for unknown scheduled tasks, scripts, or firewall rules:

/system scheduler print
/system script print
/ip firewall filter print
/ip socks print       # SOCKS proxy — sign of Mēris botnet infection

Check for unknown users:

/user print

If you find SOCKS proxy enabled or unknown scripts, the device has likely been compromised. Perform a full netinstall (clean install) rather than just upgrading.

The Mēris Botnet Connection

In 2021, researchers found that devices exploited via CVE-2018-14847 were being recruited into the Mēris botnet — a massive DDoS-as-a-service platform. Infected devices had:

• SOCKS4 proxies enabled on port 5678
• Persistent scripts surviving reboots
• Scheduled tasks calling out to C2 servers

Lessons Learned

1. Keep RouterOS updated — this exploit was patched in April 2018 but millions of devices ran unpatched for years.
2. Never expose Winbox to the internet.
3. Monitor for unexpected configuration changes.
4. Segment management traffic to a dedicated VLAN.