CVE-2019-20215 – This vulnerability allows unauthenticated remot... (How to Fix)

Q: What is the severity of CVE-2019-20215?

CVE-2019-20215 has a CVSS score of 9.8 (CRITICAL). This vulnerability allows unauthenticated remote attackers to execute arbitrary operating system commands on D-Link DIR-859 routers. Attackers can exploit the Simple Service Discovery Protocol (SSDP) implementation by sending specially crafted M-SEARCH requests with malicious urn: values containing shell metacharacters. This affects all users of vulnerable D-Link DIR-859 router firmware versions.

📋 TL;DR

This vulnerability allows unauthenticated remote attackers to execute arbitrary operating system commands on D-Link DIR-859 routers. Attackers can exploit the Simple Service Discovery Protocol (SSDP) implementation by sending specially crafted M-SEARCH requests with malicious urn: values containing shell metacharacters. This affects all users of vulnerable D-Link DIR-859 router firmware versions.

💻 Affected Systems

Products:

D-Link DIR-859

Versions: 1.05 and 1.06B01 Beta01

Operating Systems: Embedded Linux (router firmware)

Default Config Vulnerable: ⚠️ Yes

Notes: All default configurations are vulnerable as the SSDP service runs by default on port 1900/udp.

📦 What is this software?

Dir 859 Firmware by Dlink

View all CVEs affecting Dir 859 Firmware →

Dir 859 Firmware by Dlink

View all CVEs affecting Dir 859 Firmware →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete compromise of the router allowing attackers to install persistent backdoors, intercept all network traffic, pivot to internal network devices, and use the router as a botnet node.

🟠

Likely Case

Router takeover leading to DNS hijacking, credential theft from network traffic, and installation of cryptocurrency miners or other malware.

🟢

If Mitigated

Limited impact with proper network segmentation and firewall rules blocking SSDP traffic from untrusted sources.

🌐 Internet-Facing: HIGH - Routers are typically internet-facing devices, and the exploit requires no authentication, making them easy targets for automated scanning and exploitation.

🏢 Internal Only: MEDIUM - While less likely to be targeted from internal networks, the vulnerability still exists and could be exploited by compromised internal devices.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: CONFIRMED

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Multiple public exploit scripts are available that require minimal technical skill to use. The vulnerability is actively exploited in the wild.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 1.07 or later

Vendor Advisory: https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10147

Restart Required: Yes

Instructions:

1. Log into router admin interface. 2. Navigate to Firmware Update section. 3. Download firmware version 1.07 or later from D-Link support site. 4. Upload and install the firmware. 5. Reboot the router after installation completes.

🔧 Temporary Workarounds

Block SSDP traffic at firewall

linux

Prevent exploitation by blocking SSDP (port 1900/udp) traffic from untrusted networks.

iptables -A INPUT -p udp --dport 1900 -j DROP

Disable UPnP/SSDP service

all

Turn off the vulnerable SSDP service if not required for network functionality.

Check router admin interface for UPnP/SSDP settings and disable

🧯 If You Can't Patch

Replace vulnerable router with a different model that is not affected
Implement strict network segmentation to isolate the router from critical internal resources

🔍 How to Verify

Check if Vulnerable:

Check router firmware version in admin interface or use nmap to scan for SSDP service on port 1900/udp and attempt exploitation with public PoC scripts.

Check Version:

Check router web interface at http://router-ip/ or use telnet/ssh if enabled: cat /etc/version

Verify Fix Applied:

Verify firmware version is 1.07 or later in router admin interface and test that SSDP exploitation attempts no longer succeed.

📡 Detection & Monitoring

Log Indicators:

Unusual SSDP M-SEARCH requests with urn: containing shell metacharacters
Multiple failed command execution attempts in system logs
Unexpected process creation or network connections from router

Network Indicators:

SSDP traffic from unexpected sources, especially with malformed urn: values
Outbound connections from router to suspicious IPs or domains

SIEM Query:

source="router.logs" AND ("M-SEARCH" AND "urn:" AND ("|" OR ";" OR "&" OR "`"))

📊 Metadata

CVE ID: CVE-2019-20215

CVSS v3 Score: 9.8 (CRITICAL)

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

CWE: CWE-78

Published: January 29, 2020

Last Updated: November 21, 2024

🔗 References

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