CVE-2019-19940 – This vulnerability allows remote authenticated ... (How to Fix)

📋 TL;DR

This vulnerability allows remote authenticated users to execute arbitrary commands via command injection in text-oriented interfaces (telnet, SSH) of Swisscom Centro Grande routers. Attackers with valid credentials can exploit improper input sanitization to gain unauthorized command execution. Affected users are those with Swisscom Centro Grande routers running vulnerable firmware versions.

💻 Affected Systems

Products:

Swisscom Centro Grande

Versions: All versions before 6.16.12

Operating Systems: Router firmware

Default Config Vulnerable: ⚠️ Yes

Notes: Requires authenticated access to telnet or SSH interfaces. Default credentials may increase risk.

📦 What is this software?

Centro Grande Firmware by Swisscom

View all CVEs affecting Centro Grande Firmware →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Full router compromise allowing attacker to intercept all network traffic, modify router configuration, install persistent backdoors, and pivot to internal network devices.

🟠

Likely Case

Router takeover leading to network eavesdropping, DNS hijacking, credential theft, and disruption of internet services.

🟢

If Mitigated

Limited impact if strong authentication controls, network segmentation, and proper input validation are implemented.

🌐 Internet-Facing: HIGH

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: LOW

Exploitation requires valid credentials but command injection is straightforward once authenticated.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 6.16.12

Vendor Advisory: https://www.swisscom.ch/content/dam/swisscom/de/about/nachhaltigkeit/digitale-schweiz/sicherheit/bug-bounty/files/cve-2019-19940ff.txt

Restart Required: Yes

Instructions:

1. Log into router admin interface
2. Navigate to firmware update section
3. Check for and install version 6.16.12 or later
4. Reboot router after update completes

🔧 Temporary Workarounds

Disable Remote Management

all

Disable telnet and SSH access from external networks

Restrict Access with Firewall Rules

all

Limit telnet/SSH access to trusted IP addresses only

🧯 If You Can't Patch

Implement strong authentication with complex passwords and multi-factor authentication if supported
Segment router management interface to isolated VLAN with strict access controls

🔍 How to Verify

Check if Vulnerable:

Check router firmware version via admin web interface or SSH/telnet login banner

Check Version:

ssh admin@router-ip 'show version' or check web admin interface system info

Verify Fix Applied:

Confirm firmware version is 6.16.12 or later in router admin interface

📡 Detection & Monitoring

Log Indicators:

Unusual command execution in router logs
Multiple failed authentication attempts followed by successful login
Suspicious commands in telnet/SSH session logs

Network Indicators:

Unusual outbound connections from router
DNS queries to suspicious domains from router
Unexpected port scans originating from router

SIEM Query:

source="router_logs" AND ("command injection" OR "arbitrary command" OR suspicious shell commands)

📊 Metadata

CVE ID: CVE-2019-19940

CVSS v3 Score: 7.2 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-78

Published: March 16, 2020

Last Updated: November 21, 2024

🔗 References

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