I have found multiple vulnerabilities in D-Link router httpd server. These vulnerabilities are present in multiple D-Link types of routers. All three taken together allow to take a full control over te router including code execution.

1. Directory Traversal

CVE: CVE-2018-10822

CVSS v3: 8.6
AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Description: Directory traversal vulnerability in the web interface on D-Link routers:

  • DWR-116 through 1.06,
  • DIR-140L through 1.02,
  • DIR-640L through 1.02,
  • DWR-512 through 2.02,
  • DWR-712 through 2.02,
  • DWR-912 through 2.02,
  • DWR-921 through 2.02,
  • DWR-111 through 1.01,
  • and probably others with the same type of firmware

allows remote attackers to read arbitrary files via a /.. or // after “GET /uir” in an HTTP request.

NOTE: this vulnerability exists because of an incorrect fix for CVE-2017-6190.

PoC:

$ curl http://routerip/uir//etc/passwd

The vulnerability can be used retrieve administrative password using the other disclosed vulnerability - CVE-2018-10824.

This vulnerability was reported previously by Patryk Bogdan in CVE-2017-6190 but he reported it is fixed in certain release but unfortunately it is still present in even newer releases. The vulnerability is also present in other D-Link routers and can be exploited not only (as the original author stated) by double dot but also absolutely using double slash.

2. Password stored in plaintext

CVE: CVE-2018-10824

Description:

An issue was discovered on D-Link routers:

  • DWR-116 through 1.06,
  • DIR-140L through 1.02,
  • DIR-640L through 1.02,
  • DWR-512 through 2.02,
  • DWR-712 through 2.02,
  • DWR-912 through 2.02,
  • DWR-921 through 2.02,
  • DWR-111 through 1.01,
  • and probably others with the same type of firmware.

NOTE: I have changed the filename in description to XXX because the vendor leaves some EOL routers unpatched and the attack is too simple

The administrative password is stored in plaintext in the /tmp/XXX/0 file. An attacker having a directory traversal (or LFI) can easily get full router access.

PoC using the directory traversal vulnerability disclosed above - CVE-2018-10822

$ curl http://routerip/uir//tmp/XXX/0

This command returns a binary config file which contains admin username and password as well as many other router configuration settings. By using the directory traversal vulnerability it is possible to read the file without authentication.

3. Shell command injection

CVE: CVE-2018-10823

CVSS v3: 9.1
AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Description: An issue was discovered on D-Link routers:

  • DWR-116 through 1.06,
  • DWR-512 through 2.02,
  • DWR-712 through 2.02,
  • DWR-912 through 2.02,
  • DWR-921 through 2.02,
  • DWR-111 through 1.01,
  • and probably others with the same type of firmware.

An authenticated attacker may execute arbitrary code by injecting the shell command into the chkisg.htm page Sip parameter. This allows for full control over the device internals.

PoC:

  1. Login to the router.
  2. Request the following URL after login: 
    $ curl http://routerip/chkisg.htm%3FSip%3D1.1.1.1%20%7C%20cat%20%2Fetc%2Fpasswd
  3. See the passwd file contents in the response.

Exploiting all together

Taking all the three together it is easy to gain full router control including arbitrary code execution.

Suggested CVSS v3 for all three (1-3): 10.0
AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Video:

Timeline:

  • 09.05.2018 - vendor notified
  • 06.06.2018 - asked vendor about the status because of long vendor response
  • 22.06.2018 - recieved a reply that a patch will be released for DWR-116 and DWR-111, for the other devices which are EOL an announcement will be released
  • 09.09.2018 - still no reply from vendor about the patches or announcement, I have warned the vendor that if I will not get a reply in a month I will publish the disclosure
  • 12.10.2018 - disclosing the vulnerabilities


tags: CVE D-Link router CVE-2018-10822 CVE-2018-10823 CVE-2018-10824