lighttpd before 1.4.26, and 1.5.x, allocates a buffer for each read operation that occurs for a request, which allows remote attackers to cause a denial of service (memory consumption) by breaking a request into small pieces that are sent at a slow rate.
https://exchange.xforce.ibmcloud.com/vulnerabilities/56038
http://www.vupen.com/english/advisories/2011/0172
http://www.openwall.com/lists/oss-security/2010/02/01/8
http://www.debian.org/security/2010/dsa-1987
http://security.gentoo.org/glsa/glsa-201006-17.xml
http://secunia.com/advisories/39765
http://secunia.com/advisories/38403
http://redmine.lighttpd.net/projects/lighttpd/repository/revisions/2711
http://redmine.lighttpd.net/projects/lighttpd/repository/revisions/2710
http://redmine.lighttpd.net/issues/2147
http://lists.opensuse.org/opensuse-security-announce/2010-02/msg00003.html
http://lists.fedoraproject.org/pipermail/package-announce/2010-May/041307.html
http://lists.fedoraproject.org/pipermail/package-announce/2010-May/041296.html
http://lists.fedoraproject.org/pipermail/package-announce/2010-May/041264.html
http://download.lighttpd.net/lighttpd/security/lighttpd_sa_2010_01.txt
http://download.lighttpd.net/lighttpd/security/lighttpd-1.5_fix_slow_request_dos.patch
http://download.lighttpd.net/lighttpd/security/lighttpd-1.4.x_fix_slow_request_dos.patch
http://blogs.sun.com/security/entry/cve_2010_0295_vulnerability_in