The Seattle, Wash.-based RealNetworks Inc. said the flaws can be exploited by remote attackers to execute arbitrary commands with the privileges of the logged-in user.
The company issued a high-risk alert and confirmed that all four flaws affect RealPlayer 10 and 10.5, RealOne Player versions 1 and 2 and RealPlayer 8.
RealPlayer Enterprise, the configurable version of RealPlayer designed for enterprise deployments, the Rhapsody 3 music service and the open-source Linux and Helix versions are also affected, the company warned.
The most serious of the four flaws could allow an attacker to create a malicious MP3 file to allow the overwriting of a local file or execution of an ActiveX control on a vulnerable machine.
RealNetworks said a malicious RealMedia file that used RealText could also be used as an attack mechanism to cause a heap overflow. This could allow an attacker to execute arbitrary code on a target machine.
A third vulnerability was described as buffer-overflow error in the "vidplin.dll" file that does not properly handle specially crafted AVI files. This could be exploited via malicious Web sites to execute arbitrary commands with the privileges of the logged-in user, RealNetworks said.
The company said a fourth vulnerability could be combined with default settings of earlier Internet Explorer browsers and exploited by a malicious Web site to create a local HTML file and then trigger an RM file to play which would then reference the local HTML file.
Security experts have long warned that flaws in desktop media players present a lucrative target because, in most cases, the software sits behind perimeter firewalls.
"If you are a RealPlayer user, you want to take this seriously and apply the updates," said Marc Maiffret, co-founder and chief hacking officer at eEye Digital Security, a private research outfit credited with reporting the RealPlayer flaws.
In an interview with Ziff Davis Internet News, Maiffret said the flaws could easily be exploited to take over a machine with minimal user interaction. "Anyone that looks at a movie being sent through e-mail or goes to a Web page with an embedded movie can have their system compromised."
Maiffret said code execution holes in RealPlayer should be taken just as seriously as flaws in Microsoft Windows products. "[RealPlayer] is very common with computer OEMs. It may not be a Windows default, but its preinstalled on many popular brands sold over the counter," he added.
In its advisory, RealNetworks said Windows users can apply the updates via the "Tools > Check for Updates" feature of the software.
The company has posted separate instructions for updating RealPlayer Enterprise.