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Subject: Caldera Security Advisory SA-1998.31: Apache Denial of Service

Topic: Apache Denial of Service problem
Advisory issue date: August 12 1998


I. Problem Description

	There is a vulnerability in the apache web server where
	a remote user can cause apache to allocate large amounts
	of memory. If there is a resource limit on the amount
	of memory the server may use, it will abort when reaching
	this limit. If there is no limit, the server will continue
	allocating memory until the machine starts thrashing, rendering
	it unusable.

	This vulnerability has been published on bugtraq, including
	an exploit program.


II. Impact

Description:

	Remote users can render you web server inaccessible.

Vulnerable Systems:

	OpenLinux 1.0, 1.1, & 1.2 systems.


III. Solution

Workaround:

	The following workaround sets resource limit on httpd's
	memory usage. Any attack on your server will still disable
	your web service, but at least your machine is still usable
	so that you can restart the web server.

	Edit the /etc/httpd/apache/conf/httpd.conf and set resource
	limits that keep the http server from consuming extreme amounts
	of memory. For instance, the following will keep each httpd
	process from using more that roughly 64 MB of data:

	RLimitMem 64000000 64000000

Correction:

        The proper solution is to upgrade to the apache-1.3.1-1
	package. 

        They can be found on Caldera's FTP site at:
	ftp://ftp.caldera.com/pub/OpenLinux/updates/1.2/012/RPMS

        The corresponding source code can be found at:
	ftp://ftp.caldera.com/pub/OpenLinux/updates/1.2/012/SRPMS

	The MD5 checksums (from the "md5sum" command) for these
	packages are:

d6583c2ae3b604af1ac05d2cfebd0a2d  apache-1.3.1-1.i386.rpm
368c0af1b0b62dc064e996487469611d  apache-1.3.1-1.src.rpm
3df3590ae0693cf8d2885a04e08ab431  apache-docs-1.3.1-1.i386.rpm

        Upgrade with the following commands:

	rpm -q apache && rpm -U RPMS/apache-1.3.1-1.i386.rpm
	rpm -q apache-doc && rpm -U RPMS/apache-doc-1.3.1-1.i386.rpm


IV. References

        This and other Caldera security resources are located at:
	http://www.caldera.com/news/security/index.html


        This security fix closes Caldera's internal Problem Report 4082.


V. PGP Signature

	This message was signed with the PGP key for security@caldera.com.

	This key can be obtained from:
		ftp://ftp.caldera.com/pub/pgp-keys/

	Or on an OpenLinux CDROM under:
		/OpenLinux/pgp-keys/



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