The mod_dav module in Apache 2.0.50 and earlier allows remote attackers to cause a denial of service (child process crash) via a certain sequence of LOCK requests for a location that allows WebDAV authoring access.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A9588
https://github.com/Live-Hack-CVE/CVE-2004-0809
https://euvd.enisa.europa.eu/vulnerability/EUVD-2004-0807
http://www.trustix.org/errata/2004/0047/
http://www.mandrakesecure.net/en/advisories/advisory.php?name=MDKSA-2004:096
http://www.gentoo.org/security/en/glsa/glsa-200409-21.xml
http://www.debian.org/security/2004/dsa-558
http://cvs.apache.org/viewcvs.cgi/httpd-2.0/modules/dav/fs/lock.c?r1=1.32&r2=1.33