The Apache Software Foundation has rushed to release update 2.0.45 to its web server application to fix an as yet undisclosed Denial of Service (DoS) vulnerability.

The foundation warned that all versions of Apache 2 through to 2.0.44 contained a serious DoS flaw discovered discovered by David Endler, director of technical intelligence at security intelligence firm iDefense.

Details of the flaw will not be published until after 7 April, but Apache has advised all users to patch their systems before then.

Apache said that the new release is intended "principally as a security and bug fix release", as it also includes fixes for a number of smaller scale security threats.

But OS2 users received an ominous warning when Apache confirmed that a known DoS vulnerability for the platform will remain open even after the patch has been applied.

OS2 users will have to wait for 2.0.46 to get properly patched, as Apache said that this week's announcement was "too important" to delay.

Apache is the most popular web server on the market, with about 63 per cent of connected businesses using the software.

Updates from Apache can be downloaded here.