CVE-2020-17469

An issue was discovered in FNET through 4.6.4. The code for IPv6 fragment reassembly tries to access a previous fragment starting from a network incoming fragment that still doesn't have a reference to the previous one (which supposedly resides in the reassembly list). When faced with an incoming fragment that belongs to a non-empty fragment list, IPv6 reassembly must check that there are no empty holes between the fragments: this leads to an uninitialized pointer dereference in _fnet_ip6_reassembly in fnet_ip6.c, and causes Denial-of-Service.

An issue was discovered in FNET through 4.6.4. The code for IPv6 fragment reassembly tries to access a previous fragment starting from a network incoming fragment that still doesn't have a reference to the previous one (which supposedly resides in the reassembly list). When faced with an incoming fragment that belongs to a non-empty fragment list, IPv6 reassembly must check that there are no empty holes between the fragments: this leads to an uninitialized pointer dereference in _fnet_ip6_reassembly in fnet_ip6.c, and causes Denial-of-Service.

Se detectó un problema en FNET versiones hasta 4.6.4. El código para el reensamblaje de fragmentos IPv6 intenta acceder a un fragmento anterior a partir de un fragmento entrante de red que aún no cuenta con una referencia al anterior (que supuestamente reside en la lista de reensamblado). Cuando se enfrenta a un fragmento entrante que pertenece a una lista de fragmentos no vacíos, el reensamblaje de IPv6 debe comprobar que no haya huecos vacíos entre los fragmentos: esto conlleva a una desreferencia del puntero no inicializado en la función _fnet_ip6_reassembly en el archivo fnet_ip6.c, y causa una Denegación de Servicio