Symantec has issued patches to fix a "high impact" security hole that affects almost every product it currently sells.

According to security rival ISS, which unearthed the vulnerability, the problem lies with the DEC2EXE module in the Symantec Anti-Virus Library, a part of the virus detection engine that makes it possible to detect malware inside executable files compressed using the freeware UPX (Ultimate Packer for eXecuteables) format.

The vulnerable module fails to properly check within files when looking for viruses, a flaw that could allow an attacker to cause an software "heap overflow" using a specially crafted UPX file. ISS stated that this could, in turn, give an attacker unauthorized access to a network or its client PCs, as well as confidential information.

The company has posted an extensive list of affected products on its website, which includes its most popular programs for PC, Apple Mac, Linux and AS400 platforms, and even antispam software from Brightmail, a company acquired last year. Those versions not affected are mainly older, non-current versions of products or those updated most recently.

In an attempt to calm anxiety that a serious problem could affect almost its whole product line, Symantec emphasized that it had started removing the DEC2EXE module from its software before the issue came to light.

"Prior to ISS contacting Symantec with this vulnerability, Symantec had already removed the DEC2EXE engine from the scan engine upgrades implemented in the majority of Symantec products. Also, Symantec had planned the DEC2EXE engine removal from all affected Symantec product versions during upcoming maintenance updates," it stated on the company website.