Hackers have once again turned to PDF files to spread their wares, this time assaulting a zero-day flaw affecting Adobe Reader and Acrobat.

Fortunately, the unpatched bug is on the company’s radar, and fixes for Adobe Reader 9 and Acrobat 9 are slated to be available March 11. Updates for earlier versions will come later, company officials said in an advisory.

The bug is due to an error in the parsing of certain structures in PDF files. If exploited successfully, the bug could allow a hacker to take complete control of a vulnerable system.

“In parsing a specially-crafted embedded object, a bug in the reader allowed the attacker to overwrite memory at an arbitrary location,” blogged McAfee researcher Geok Meng Ong. “The attacks, found in the field, use the infamous heap spray method via JavaScript to achieve control of code execution.”

“While the distribution of this exploit thus far appears to be targeted, new variants are expected as more information is made public,” the researcher continued. “As with the Conficker experience, the lack of good patch management is a very worrying trend that deserves more attention from IT security practitioners. Adobe is expected to release a patch very soon.”

In the meantime, security researchers at the Shadowserver Foundation recommend users consider disabling JavaScript. Symantec also recommended Adobe users keep their antivirus up-to-date.

“While we continue to investigate this issue, customers are advised to follow best practices and only open email attachments from people they trust,” blogged Symantec researcher Patrick Fitzgerald. “Enabling DEP (Data Execution Prevention) for Adobe Reader will also help prevent this type of attack.”