![]() ![]() Note: Cookies are shared between tabs and popped up browser windows. ![]() The SID is stored in many places (browser history log, web server log, proxy logs.The SID is leaked to other people as users cut & paste "interesting links" from the address bar into chats, forums, communities, etc.Session identifiers in URL (query string, GET variables) or POST variables are not recommended as they simplify this attack – it is easy to make links or forms that set GET / POST variables. Mallory is thus able to ghost the session from their original login, scraping data and executing operations as 'A1ice' on 'If Alice was successfully duped and saved her credit card to the account, Mallory might then make purchases using that card.Ĭountermeasures Do not accept session identifiers from GET / POST variables Mallory then entraps Alice with a URL from which fixates that session cookie in Alice's browser (as described above) and redirects to for finalizing a particular transaction (or, in fact, broader use). forms or registration) as well as the ability to feed the user an established session to bypass the login completely.Ĭonsider, for example, that Mallory may create a user A1ice on and login that user to capture a current, valid session identifier. This includes scenarios exploiting both the unauthenticated scenarios (e.g. For example, Mallory may provide a URL from their evil site, fixating a session into an unauthenticated scenario, and use those techniques to exploit their target. It is not essential that a user login to exploit session fixation attacks and, although these unauthenticated attacks are not constrained to cross-sub-domain cookie attacks, the implications of sub-domain attacks are relevant to these unauthenticated scenarios. When this attack is complete, Mallory can gain access to as Alice. If Alice now logs on, Mallory can use her account.When Alice visits this cookie will be sent with the request and Alice will have the session specified by Mallory's cookie.A visit to sets a session cookie with the domain.One such party, Mallory, who now controls, lures Alice to his site.A web site hands out subdomains to untrusted third parties.Rather, it relies on the fact that wildcard cookies can be set by a subdomain and, that those cookies may affect other subdomains. This type of attack is similar to a cross-site cookie attack except that, it does not rely on the vulnerability of the user's browser. Alice logs on, with fixated session identifier SID=0D6441FEA4496C2.Īttacks using cross-subdomain cookie.Mallory is now able to send Alice an e-mail: "Check out this new cool feature on our bank.For example, the server may respond: Set-Cookie: SID=0D6441FEA4496C2. Mallory visits and checks which SID is returned.Mallory visits and now has unlimited access to Alice's account.Īttack using server generated SID Ī misconception is that if a server only accepts server-generated session identifiers, it is safe from fixation.The usual log-on screen pops up, and Alice logs on. Mallory is trying to fixate the SID to I_WILL_KNOW_THE_SID. Mallory sends Alice an e-mail: "Hey, check this out, there is a cool new account summary feature on our bank, ".Mallory has determined that accepts any session identifier, accepts session identifiers from query strings and has no security validation.Mallory intends to target Alice's money from her bank.Īlice has a reasonable level of trust in Mallory, and will visit links Mallory sends her. Most session fixation attacks are web based, and most rely on session identifiers being accepted from URLs ( query string) or POST data. In computer network security, session fixation attacks attempt to exploit the vulnerability of a system that allows one person to fixate (find or set) another person's session identifier. ( April 2012) ( Learn how and when to remove this template message) Please help to improve this article by introducing more precise citations. This article includes a list of general references, but it lacks sufficient corresponding inline citations. ![]()
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