Apache httpd 1.3.37, 2.0.59, and 2.2.4 with the Prefork MPM module, allows local users to cause a denial of service by modifying the worker_score and process_score arrays to reference an arbitrary process ID, which is sent a SIGUSR1 signal from the master process, aka "SIGUSR1 killer."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11589
https://exchange.xforce.ibmcloud.com/vulnerabilities/35095
http://www.vupen.com/english/advisories/2008/0233
http://www.vupen.com/english/advisories/2007/4305
http://www.vupen.com/english/advisories/2007/3494
http://www.vupen.com/english/advisories/2007/3420
http://www.vupen.com/english/advisories/2007/3283
http://www.vupen.com/english/advisories/2007/3100
http://www.vupen.com/english/advisories/2007/2727
http://www.ubuntu.com/usn/usn-499-1
http://www.securityfocus.com/bid/24215
http://www.securityfocus.com/archive/1/505990/100/0/threaded
http://www.securityfocus.com/archive/1/471832/100/0/threaded
http://www.securityfocus.com/archive/1/469899/100/0/threaded
http://www.redhat.com/support/errata/RHSA-2008-0261.html
http://www.redhat.com/support/errata/RHSA-2007-0662.html
http://www.redhat.com/support/errata/RHSA-2007-0557.html
http://www.redhat.com/errata/RHSA-2007-0532.html
http://www.redhat.com/archives/fedora-package-announce/2007-September/msg00320.html
http://www.fujitsu.com/global/support/software/security/products-f/interstage-200802e.html
http://www-1.ibm.com/support/search.wss?rs=0&q=PK50467&apar=only
http://www-1.ibm.com/support/docview.wss?uid=swg1PK53984
http://www-1.ibm.com/support/docview.wss?uid=swg1PK52702
http://svn.apache.org/viewvc?view=rev&revision=547987
http://support.avaya.com/elmodocs2/security/ASA-2007-363.htm
http://support.avaya.com/elmodocs2/security/ASA-2007-353.htm
http://security.psnc.pl/files/apache_report.pdf
http://security.gentoo.org/glsa/glsa-200711-06.xml
http://secunia.com/advisories/28606
http://secunia.com/advisories/28224
http://secunia.com/advisories/28212
http://secunia.com/advisories/27732
http://secunia.com/advisories/27563
http://secunia.com/advisories/27209
http://secunia.com/advisories/27121
http://secunia.com/advisories/26993
http://secunia.com/advisories/26842
http://secunia.com/advisories/26822
http://secunia.com/advisories/26790
http://secunia.com/advisories/26759
http://secunia.com/advisories/26611
http://secunia.com/advisories/26508
http://secunia.com/advisories/26443
http://secunia.com/advisories/26273
http://secunia.com/advisories/26211
http://secunia.com/advisories/25920
http://secunia.com/advisories/25830
http://secunia.com/advisories/25827
http://rhn.redhat.com/errata/RHSA-2007-0556.html
http://marc.info/?l=apache-httpd-dev&m=118252946632447&w=2
http://lists.vmware.com/pipermail/security-announce/2009/000062.html
http://httpd.apache.org/security/vulnerabilities_22.html
http://httpd.apache.org/security/vulnerabilities_20.html
http://httpd.apache.org/security/vulnerabilities_13.html
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c01182588