Polipo 1.0.4, and possibly other versions, allows remote attackers to cause a denial of service (crash) via a request with a Cache-Control header that lacks a value for the max-age field, which triggers a segmentation fault in the httpParseHeaders function in http_parse.c, and possibly other unspecified vectors.
http://www.securityfocus.com/bid/37463
http://www.debian.org/security/2010/dsa-2002
http://secunia.com/advisories/38647
http://secunia.com/advisories/37607
http://groups.google.com/group/linux.debian.bugs.dist/browse_thread/thread/dca6877a8117f0df