The ap_pregsub function in server/util.c in the Apache HTTP Server 2.0.x through 2.0.64 and 2.2.x through 2.2.21, when the mod_setenvif module is enabled, does not restrict the size of values of environment variables, which allows local users to cause a denial of service (memory consumption or NULL pointer dereference) via a .htaccess file with a crafted SetEnvIf directive, in conjunction with a crafted HTTP request header, related to (1) the "len +=" statement and (2) the apr_pcalloc function call, a different vulnerability than CVE-2011-3607.

References

• https://nvd.nist.gov/vuln/detail/CVE-2011-4415
• http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c03360041
• http://www.gossamer-threads.com/lists/apache/dev/403775
• http://www.halfdog.net/Security/2011/ApacheModSetEnvIfIntegerOverflow/DemoExploit.html
• http://www.halfdog.net/Security/2011/ApacheModSetEnvIfIntegerOverflow