CVE-2008-3873

Vulnerability

The System.setClipboard method in ActionScript within Adobe Flash Player version 9.0.124.0 and earlier allows a remote attacker to populate the user's clipboard with an arbitrary URL. This flaw requires no user interaction to set the clipboard content, nor does it prompt the user for consent. The vulnerability was exploited in the wild in August 2008 [1][2].

Exploitation

An attacker hosts a malicious SWF file that, when rendered by the victim's browser, invokes System.setClipboard to copy a URL to the system clipboard. The victim does not need to click, type, or otherwise interact with the content; merely viewing the web page containing the SWF triggers the clipboard write. The attacker can choose a URL that is difficult to delete or that appears enticing, increasing the likelihood that the victim later pastes it into their browser's address bar [1].

Impact

A successful attack places an attacker-controlled URL on the victim's clipboard without their knowledge or consent. If the victim subsequently pastes the clipboard content into their browser's address bar, they may navigate to a malicious site that serves malware, performs phishing, or conducts other harmful activity. The compromise is limited to URL manipulation and potential redirection; no code execution or privilege escalation is achieved directly by this flaw [1].

Mitigation

Adobe released updates to Flash Player after the discovery of this issue. Red Hat issued RHSA-2008:0980 to update the flash-plugin package for Red Hat Enterprise Linux, addressing CVE-2008-3873 among other vulnerabilities [2]. Sun Microsystems also provided a fix through Sun Alert 248586 for Solaris systems [4]. Users should upgrade to a patched version of Adobe Flash Player (9.0.124.0 or later). No workaround exists other than disabling Flash Player entirely.