D-Link DIR-859 Router Command Execution
CVE-2019-17621 is a critical-severity improper neutralization of special elements used in an OS command vulnerability in Dir-859 Firmware from D-Link, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Dir-859 Firmware versions: 1.05b03 and earlier; 1.06b01. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on June 29, 2023, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Check which version of Dir-859 Firmware you run against the affected versions below, and install the vendor's latest release.
- CISA's required action: Apply updates per vendor instructions or discontinue use of the product if updates are unavailable.
- Read the advisory on supportannouncement.us.dlink.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| D-Link | Dir-859 Firmware | 1.05b03 and earlier; 1.06b01 | Not stated |
| D-Link | Dir-822 Firmware | 2.03b01 and earlier; 3.12b04 and earlier | Not stated |
| D-Link | Dir-823 Firmware | 1.00b06 and earlier; 1.00b06 | Not stated |
| D-Link | Dir-865l Firmware | 1.07b01 and earlier | Not stated |
| D-Link | Dir-868l Firmware | 1.12b04 and earlier; 2.05b02 and earlier | Not stated |
| D-Link | Dir-869 Firmware | 1.03b02 and earlier; 1.03b02 | Not stated |
| D-Link | Dir-880l Firmware | 1.08b04 and earlier | Not stated |
| D-Link | Dir-890l Firmware | 1.11b01 and earlier; 1.11b01 | Not stated |
| D-Link | Dir-890r Firmware | 1.11b01 and earlier; 1.11b01 | Not stated |
| D-Link | Dir-885l Firmware | 1.12b05 and earlier | Not stated |
| D-Link | Dir-885r Firmware | 1.12b05 and earlier | Not stated |
| D-Link | Dir-895l Firmware | 1.12b10 and earlier | Not stated |
| D-Link | Dir-895r Firmware | 1.12b10 and earlier | Not stated |
| D-Link | Dir-818lx Firmware | Not specified in the record | Not stated |
Version data comes from NVD's product matching. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 3.1 | 9.8 | Critical | CISA (ADP) |
| CVSS 2.0 | 10.0 | High | NVD |
Official description
The UPnP endpoint URL /gena.cgi in the D-Link DIR-859 Wi-Fi router 1.05 and 1.06B01 Beta01 allows an Unauthenticated remote attacker to execute system commands as root, by sending a specially crafted HTTP SUBSCRIBE request to the UPnP service when connecting to the local network.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements used in an OS Command
The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.
How developers prevent this class of flaw
- If at all possible, use library calls rather than external processes to recreate the desired functionality.
- For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
More Improper Neutralization of Special Elements used in an OS Command vulnerabilities (CWE-78)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- ftc.gov/system/files/documents/cases/dlink_proposed_order_and_judgment_7-2-19.pdfThird Party Advisory, US Government Resource
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2019-17621US Government Resource
Technical write-ups (may include proof of concept)
- packetstormsecurity.com/files/156054/D-Link-DIR-859-Unauthenticated-Remote-Command-Execution.htmlExploit, Third Party Advisory, VDB Entry
- medium.com/%40s1kr10s/d-link-dir-859-rce-unautenticated-cve-2019-17621-en-d94b47a15104Exploit, Third Party Advisory
Other vulnerabilities in Dir-859 Firmware
- 9.8 Critical severity
D-Link DIR-859 Router Path Traversal Exploited
- 9.8 Critical severity
Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities
- 9.8 Critical severity
- 9.8 Critical severity
D-Link DNS-320 Remote Code Execution Exploited
- 8.8 High severity
Nagios XI Remote Code Execution Exploited
- 9.8 Critical severity
Webmin Command Injection Exploited
- 8.8 High severity
- 9.8 Critical severity
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