According to Symantec, the bug, which affects a range of the company's security products, is a "high" risk. Denmark security company Secunia has labelled it "highly critical."
According to an advisory issued by Secunia, the bug affects most of Symantec's products, including enterprise and home user versions of Symantec AntiVirus, Symantec Norton AntiVirus and Symantec Norton Internet Security, across the Windows and Macintosh platforms.
The vulnerability is within Symantec AntiVirus Library, which provides file format support for virus analysis. "During decompression of RAR files, Symantec is vulnerable to multiple heap overflows allowing attackers complete control of the system(s) being protected," said security consultant Alex Wheeler, who first discovered the flaw. "These vulnerabilities can be exploited remotely, without user interaction, in default configurations through common protocols such as SMTP."
RAR is a native format for WinRAR, which is used to compress and decompress data. So far, the vulnerability has been reported in Dec2Rar.dll version 18.104.22.168 and, according to Wheeler, potentially affects all Symantec products that use the DLL. The full list of products affected can be seen here.
Symantec has not yet released a patch to address this problem. In the meantime, Wheeler recommends that users "disable scanning of RAR-compressed files until the vulnerable code is fixed."
This is not the first vulnerability Wheeler has discovered. In October, he highlighted a similar flaw in Kaspersky Lab's antivirus software, which was later acknowledged by the company. Again, it was a heap overflow vulnerability.
In February, he found a different heap overflow vulnerability in Symantec's antivirus software.
ZDNet UK's Colin Barker reported from London. For more coverage from ZDNet UK, click here.