Antipiracy tool leads to DoS in Office for Mac

A security vulnerability in an antipiracy tool included in Microsoft Corp.'s Office v. X for the Macintosh can allow an attacker to crash applications in Office, Microsoft said in a bug alert Thursday. The company has released a patch to fix the problem.

The vulnerability is in the Network Product Identification Checker component of Office v. X, a tool which checks the local network that the copy of Office is running on for other copies using the same Product Identifier (PID), a number similar to a serial number, Microsoft said. Each copy of Office v. X periodically "announces" its PID to the network and if two copies of Office v. X on a single network share the same PID, the application shuts down.

When a specially formulated announcement is sent to a machine or over the network, the Network PID Check component incorrectly handles it and can cause Office v. X to crash, the company said. When such a specially formulated packet is sent, only the first application opened after Office is launched will crash, though unsaved data could be lost, Microsoft said. The attack could be directed against a single machine, using its IP (Internet Protocol) address, or against an entire local network, the company added.

The attack can be blocked, Microsoft said, by stopping certain kinds of traffic at the firewall and applying the patch. The attack has no further impact beyond crashing Office, Microsoft said.

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