Open-source image format vulnerabilities could allow intruders to compromise computers running Mac OS X.

Windows PCs and computers running Linux are also vulnerable to such attacks, according to a report

The security issues appear in a library supporting the portable network graphics (PNG) format, which is used by the Mozilla, Internet Explorer, Netscape and Opera browsers as well as a number of email clients – including Apple Mail.

Independent security researcher Chris Evans discovered the issues. He told Silicon: "The most critical issue, a memory problem known as a buffer overflow, could allow specially created PNG graphics to execute a malicious program when the application loads the image.

"A scarier possibility is targeted exploitation by emailing a nasty PNG to someone who uses a graphical email client to decode images."

Security information service Secunia has rated the vulnerabilities highly critical. "The vulnerabilities can be exploited by tricking a computer user into visiting a malicious website or viewing an email with an affected application linked to libPNG," Secunia said.