libxml2 before 2.7.8, as used in Google Chrome before 7.0.517.44, Apple Safari 5.0.2 and earlier, and other products, reads from invalid memory locations during processing of malformed XPath expressions, which allows context-dependent attackers to cause a denial of service (application crash) via a crafted XML document.

Heap-based buffer overflow in the xmlParseAttValueComplex function in parser.c in libxml2 before 2.7.0 allows context-dependent attackers to cause a denial of service (crash) or execute arbitrary code via a long XML entity name.

libxml2 2.6.32 and earlier does not properly detect recursion during entity expansion in an attribute value, which allows context-dependent attackers to cause a denial of service (memory and CPU consumption) via a crafted XML document.

libxml2, possibly before 2.5.0, does not properly detect recursion during entity expansion, which allows context-dependent attackers to cause a denial of service (memory and CPU consumption) via a crafted XML document containing a large number of nested entity references, aka the "billion laughs attack."