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Multiple cross-site request forgery (CSRF) vulnerabilities in the management screen on Buffalo WHR, WZR2, WZR, WER, and BBR series routers with firmware 1.x; BHR-4RV and FS-G54 routers with firmware 2.x; and AS-100 routers allow remote attackers to hijack the authentication of administrators for requests that modify settings, as demonstrated by changing the login password.
Multiple cross-site request forgery (CSRF) vulnerabilities in the management screen on Buffalo WHR, WZR2, WZR, WER, and BBR series routers with firmware 1.x; BHR-4RV and FS-G54 routers with firmware 2.x; and AS-100 routers allow remote attackers to hijack the authentication of administrators for requests that modify settings, as demonstrated by changing the login password.
CVSS 2.0 Base Score 5.8. CVSS Attack Vector: network. CVSS Attack Complexity: medium. CVSS Vector: (AV:N/AC:M/Au:N/C:N/I:P/A:P).
This example PHP code attempts to secure the form submission process by validating that the user submitting the form has a valid session. A CSRF attack would not be prevented by this countermeasure because the attacker forges a request through the user's web browser in which a valid session already exists.
The following HTML is intended to allow a user to update a profile.
</form>profile.php contains the following code.
}//if the session is registered to a valid user then allow update
exit;// Redirect user to login page// The user session is valid, so process the request// and update the information
echo "Your profile has been successfully updated.";// read in the data from $POST and send an update// to the databaseThis code may look protected since it checks for a valid session. However, CSRF attacks can be staged from virtually any tag or HTML construct, including image tags, links, embed or object tags, or other attributes that load background images.
The attacker can then host code that will silently change the username and email address of any user that visits the page while remaining logged in to the target web application. The code might be an innocent-looking web page such as:
</form>form.submit();// send to profile.phpNotice how the form contains hidden fields, so when it is loaded into the browser, the user will not notice it. Because SendAttack() is defined in the body's onload attribute, it will be automatically called when the victim loads the web page.
Assuming that the user is already logged in to victim.example.com, profile.php will see that a valid user session has been established, then update the email address to the attacker's own address. At this stage, the user's identity has been compromised, and messages sent through this profile could be sent to the attacker's address.
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