Security researchers have uncovered "critical" security flaws in a version of the Linux kernel used by a large number of popular distributions.
The three bugs allow unauthorised users to read or write to kernel memory locations or to access certain resources in certain vservers, according to a SecurityFocus advisory.
They could be exploited by malicious, local users to cause denial of service attacks, disclose potentially sensitive information or gain "root" privileges, according to security experts.
The bug affects all versions of the Linux kernel up to version 18.104.22.168, which contains a patch. Distributions such as Ubuntu, Turbolinux, SuSE, Red Hat, Mandriva, Debian and others are affected.
The problems are within three functions in the system call fs/splice.c, according to an advisory from Secunia.
"In the 2.6.23 kernel the system call functionality has been further extended resulting in... critical vulnerabilities," said iSEC Security Research in an advisory.
Secunia disagreed about the bugs' seriousness, giving them a less critical ranking.
Exploit code for the vulnerabilities has been released publicly on the hacker site milw0rm.com, and Core Security Technologies has also developed a commercial exploit for the bugs, researchers said.
Researchers advised system administrators to update their kernels immediately.
Last month, a US Department of Homeland Security (DHS) bug-fixing scheme uncovered an average of one security glitch per 1,000 lines of code in 180 widely used open source software projects.
Secunia also previously discovered that the number of security bugs in open source Red Hat Linux operating system and Firefox browsers, far outstripped comparable products from Microsoft last year.