InterScan VirusWall 3.52 build 1462 allows remote attackers to bypass virus protection via e-mail messages with headers that violate RFC specifications by having (or missing) space characters in unexpected places (aka "space gap"), such as (1) Content-Type :", (2) "Content-Transfer-Encoding :", (3) no space before a boundary declaration, or (4) "boundary= ", which is processed by Outlook Express.