Digital media delivery firm RealNetworks has patched a potentially serious security flaw in RealPlayer and RealOne, two software products that serve as the hub of the company's streaming media business.

According to an advisory from RealNetworks, the vulnerability could allow an attacker to run arbitrary or malicious code on a user's machine.

The flaw, which is rated "highly critical" by research firm Secunia, affects RealPlayer 10.5 (prior to build 6.0.12.1056), RealPlayer 10 and RealOne Player versions 1 and 2.

RealNetworks said it had received no reports of machines compromised as a result of the vulnerability, which has been patched via the software's built-in update facility. RealPlayer and RealOne users are urged to apply the fix from the "Tools > Check for Update" feature.

The company said the specific buffer overflow exploit was discovered in DUNZIP32.DLL, a module that offers support for ZIP compressed folders in the Windows shell. A successful attacker would have to fashion a malicious skin file to cause a buffer overflow and execute arbitrary code on a customer's machine, RealNetworks said.

eEye Digital Security, which is credited with finding and reporting the flaw to RealNetworks, first discovered the DUNZIP32.DLL vulnerability in August this year. eEye said an exploitable buffer overflow occurs when a user opens a ZIP folder that contains a long file name (greater than around 0x8000 bytes).

Microsoft released a patch for the flaw in its October batch of advisories.