||ftpd in OpenBSD 4.3, FreeBSD 7.0, NetBSD 4.0, Solaris, and possibly other operating systems interprets long commands from an FTP client as multiple commands, which allows remote attackers to conduct cross-site request forgery (CSRF) attacks and execute arbitrary FTP commands via a long ftp:// URI that leverages an existing session from the FTP client implementation in a web browser.
Cross Site Request Forgery
An attacker crafts malicious web links and distributes them (via web pages, email, etc.), typically in a targeted manner, hoping to induce users to click on the link and execute the malicious action against some third-party application. If successful, the action embedded in the malicious link will be processed and accepted by the targeted application with the users' privilege level. This type of attack leverages the persistence and implicit trust placed in user session cookies by many web applications today. In such an architecture, once the user authenticates to an application and a session cookie is created on the user's system, all following transactions for that session are authenticated using that cookie including potential actions initiated by an attacker and simply "riding" the existing session cookie.
Cross Site Identification
An attacker harvests identifying information about a victim via an active session that the victim's browser has with a social networking site. A victim may have the social networking site open in one tab or perhaps is simply using the "remember me" feature to keep his or her session with the social networking site active. An attacker induces a payload to execute in the victim's browser that transparently to the victim initiates a request to the social networking site (e.g., via available social network site APIs) to retrieve identifying information about a victim. While some of this information may be public, the attacker is able to harvest this information in context and may use it for further attacks on the user (e.g., spear phishing). In one example of an attack, an attacker may post a malicious posting that contains an image with an embedded link. The link actually requests identifying information from the social networking site. A victim who views the malicious posting in his or her browser will have sent identifying information to the attacker, as long as the victim had an active session with the social networking site. There are many other ways in which the attacker may get the payload to execute in the victim's browser mainly by finding a way to hide it in some reputable site that the victim visits. The attacker could also send the link to the victim in an e-mail and trick the victim into clicking on the link. This attack is basically a cross site request forgery attack with two main differences. First, there is no action that is performed on behalf of the user aside from harvesting information. So standard CSRF protection may not work in this situation. Second, what is important in this attack pattern is the nature of the data being harvested, which is identifying information that can be obtained and used in context. This real time harvesting of identifying information can be used as a prelude for launching real time targeted social engineering attacks on the victim.
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