14 DAY TRIAL // Researchers from security firm McAfee have identified an interesting issue that affects all versions of Adobe Reader. While the flaw can’t be leveraged to execute code, it can be successfully utilized to track when and where specially-crafted PDF documents are opened.
“When a specific PDF JavaScript API is called with the first parameter having a UNC-located resource, Adobe Reader will access that UNC resource. However, this action is normally blocked and creates a warning dialog asking for permission,” McAfee’s Haifei Li explained in a blog post.
“The danger is that if the second parameter is provided with a special value, it changes the API’s behavior. In this situation, if the UNC resource exists, we see the warning dialog. However, if the UNC resource does not exist, the warning dialog will not appear even though the TCP traffic has already gone.”
The company has identified PDFs that leverage this bug. They have been sent by an “email tracking service” provider.
For the time being, it’s uncertain if the method has been used for illegal purposes, but experts warn that it could be.
Li explains that it could be successfully applied in advanced persistent threat (APT) attacks, which usually have several phases.
This particular PDF flaw could be leveraged in the first step of the attack, the one that involves collecting as much information as possible from the victim.
“Malicious senders could exploit this vulnerability to collect sensitive information such as IP address, Internet service provider, or even the victim’s computing routine. In addition, our analysis suggests that more information could be collected by calling various PDF JavaScript APIs,” Li noted.
Adobe has been notified of the issue, but so far, there’s no patch. In the meantime, users are advised to consider disabling JavaScript in Reader.