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Is it possible to change the admin user/password remotely on a router without logging in? If yes, how so?

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Why the downvote? –  Moshe Nov 23 '10 at 18:37
    
I'd guess that someone may have downvoted you, because the question could be seen as a request for information on how to get unauthorised access to a router. Usually if you own a router (and thus have a legitimate reason to want to change the username/password) you would have physical access to it and would be able to do a factory reset which would likely take the setting back to default. I'd suggest you update your question to include some information about what circumstances require you to try to do this. –  Rоry McCune Nov 24 '10 at 13:10
    
@RoryMcCune - School, there's a router which we don't have physical access to, which a fellow student changed the admin user/pwd. –  Moshe Nov 29 '10 at 14:24
    
Maybe you could define better if you are trying to change the password in an unauthorized way or in an already authorized way. You got two answers right now, both describing each approach :) –  Chris Andrè Dale Nov 29 '10 at 18:09
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@ChrisAD - An unauthorized way. –  Moshe Nov 29 '10 at 18:14

2 Answers 2

up vote 1 down vote accepted

This ofcourse depends on which router you try on. You cant expect an exploit or security hole to work on all routers. So by exploiting a design flaw or something similar you could certinatly change a router's password.

However most vendors would try to patch something like this asap.

For example searching osvdb.org for ZyXEL produces a long list of exploits. Check it our here

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Most routers use a HTTP Basic authentication scheme.
To access any page, including the change password, the credentials would need to be sent in header.
So, you dont need to "Log In", but you would need to send your credentials. Does that count?

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So how would I do that? Can you provide some example(s)? –  Moshe Nov 22 '10 at 21:54
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Are you asking how basic authentication works? That should be a seperate question... but in short it would look like Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ== in a request header with the user/password base64 encoded. –  AviD Nov 22 '10 at 22:01
    
I will ask, but please clarify this: Are you saying that so long as there is some username/password encoded in Base64, the router should log me in? –  Moshe Nov 23 '10 at 14:18
    
Well, it would have to be the correct username/password of course. But aside from that, yes that is the way HTTP Basic AuthN works, and thats what is usually used by most routers. –  AviD Nov 23 '10 at 14:23

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