NULL Pointer Dereference allows attackers to cause a denial of service (or application crash). This only applies when lxml is used together with libxml2 2.9.10 through 2.9.14. libxml2 2.9.9 and earlier are not affected. It allows triggering crashes through forged input data, given a vulnerable code sequence in the application. The vulnerability is caused by the iterwalk function (also used by the canonicalize function). Such code shouldn't be in wide-spread use, given that parsing + iterwalk would usually be replaced with the more efficient iterparse function. However, an XML converter that serialises to C14N would also be vulnerable, for example, and there are legitimate use cases for this code sequence. If untrusted input is received (also remotely) and processed via iterwalk function, a crash can be triggered.

GNOME libxml2 is vulnerable to a buffer overflow, caused by improper bounds checking by the xmlEncodeEntitiesInternal function in libxml2/entities.c. By persuading a victim to open a specially-crafted file, a remote attacker could overflow a buffer and execute arbitrary code on the system.

GNOME libxml2 is vulnerable to a denial of service, caused by an error in xmlStringLenDecodeEntities in parser.c. An attacker could exploit this vulnerability to cause the application to enter into an infinite loop.

A memory leak was found in the xmlSchemaValidateStream function of libxml2. Applications that use this library may be vulnerable to memory not being freed leading to a denial of service. System availability is the highest threat from this vulnerability.