# Cookie Tossing
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### Description If an attacker can **control a subdomain or the domain of a company or finds an XSS in a subdomain** he will be able to perform this attack. As it was indicated in the Cookies Hacking section, when a **cookie is set to a domain (specifying it) it will be used in the domain and subdomains.** {% hint style="danger" %} Therefore, **an attacker is going to be able to set to the domain and subdomains a specific cookie doing something like** `document.cookie="session=1234; Path=/app/login; domain=.example.com"` {% endhint %} This can be dangerous as the attacker may be able to: * **Fixate the cookie of the victim to the attacker's account** so if the user doesn't notice, **he will perform the actions in the attacker's account** and the attacker may obtain some interesting information (check the history of the searches of the user in the platform, the victim may set his credit card in the account...) * If the **cookie doesn't change after login**, the attacker may just **fixate a cookie**, wait until the victim logs in and then **use that cookie to log in as the victim**. * If the **cookie is setting some initial value** (like in flask where the **cookie** may **set** the **CSRF token** of the session and this value will be maintained after the victim logs in), the **attacker may set this known value and then abuse it** (in that scenario, the attacker may then make the user perform a CSRF request as he knows the CSRF token). ### Cookie Order When a browser receives two cookies with the same name **partially affecting the same scope** (domain, subdomains and path), the **browser will send both values of the cookie** when both are valid for the request. Depending on who has **the most specific path** or which one is the **oldest one**, the browser will **set the value of the cookie first** and then the value of the other one like in: `Cookie: iduser=MoreSpecificAndOldestCookie; iduser=LessSpecific;` Most **websites will only use the first value**. Then, if an attacker wants to set a cookie it's better to set it before another one is set or set it with a more specific path. {% hint style="warning" %} Moreover, the capability to **set a cookie in a more specific path** is very interesting as you will be able to make the **victim work with his cookie except in the specific path where the malicious cookie set will be sent before**. {% endhint %} ### Protection Bypass Possible protection against this attack would be that the **web server won't accept requests with two cookies with the same name but two different values**. To bypass the scenario where the attacker is setting a cookie after the victim was already given the cookie, the attacker could cause a **cookie overflow** and then, once the **legit cookie is deleted, set the malicious one**. {% content-ref url="/pages/NZr5PtUAHCaXwVksfS1y" %} [Cookie Jar Overflow](/dashboard/pentesting-web/hacking-with-cookies/cookie-jar-overflow.md) {% endcontent-ref %} Another useful **bypass** could be to **URL encode the name of the cookie** as some protections check for 2 cookies with the same name in a request and then the server will decode the names of the cookies. ### Cookie Bomb A Cookie Tossing attack may also be used to perform a **Cookie Bomb** attack: {% content-ref url="/pages/xIuUFUlmTmMTHVDzb2RV" %} [Cookie Bomb](/dashboard/pentesting-web/hacking-with-cookies/cookie-bomb.md) {% endcontent-ref %} ### Defense**s** #### **Use the prefix `__Host` in the cookie name** * If a cookie name has this prefix, it **will only be accepted** in a Set-Cookie directive if it is marked Secure, was sent from a secure origin, does not include a Domain attribute, and has the Path attribute set to / * **This prevents subdomains from forcing a cookie to the apex domain since these cookies can be seen as "domain-locked"** ### References * [**@blueminimal**](https://twitter.com/blueminimal) * [**https://speakerdeck.com/filedescriptor/the-cookie-monster-in-your-browsers**](https://speakerdeck.com/filedescriptor/the-cookie-monster-in-your-browsers) * [**https://github.blog/2013-04-09-yummy-cookies-across-domains/**](https://github.blog/2013-04-09-yummy-cookies-across-domains/)
🎙️ HackTricks LIVE Twitch Wednesdays 5.30pm (UTC) 🎙️ - 🎥 Youtube 🎥 * Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)! * Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family) * Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com) * **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.** * **Share your hacking tricks by submitting PRs to the** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **and** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).
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