The bug exists in Adobe Reader 9.3.4 and earlier for Windows, Macintosh and Unix systems. It also exists in Adobe Acrobat versions 9.3.4 and earlier for Mac and Windows.
And, according to Adobe, the bug can be exploited to "cause a crash and potentially allow an attacker to take control of the affected system."
Adobe did not provide any other details on the vulnerability, but Secunia calls the situation "extremely critical" and that the issue is caused by "a boundary error within CoolType.dll when processing the "uniqueName" entry of SING tables in fonts and can be exploited to cause a stack-based buffer overflow by e.g. tricking a user into opening a malicious PDF file containing a specially crafted embedded font."
"Do not open untrusted files," Secunia advised.
Adobe officials did not offer a timeline for when a patch would be available.
