bgpd/bgp_attr.c in Quagga 0.98.6 and earlier, and 0.99.6 and earlier 0.99 versions, does not validate length values in the MP_REACH_NLRI and MP_UNREACH_NLRI attributes, which allows remote attackers to cause a denial of service (daemon crash or exit) via crafted UPDATE messages that trigger an assertion error or out of bounds read.