Cisco has closed a hole in its ASR 1000 line of enterprise and service provider-grade routers that could trigger denial of service.
Attackers can exploit the hole by crafting a series of packets that cause the routers to reload and cut net services.
The Borg says it has not witnessed attacks in the wild.
"A vulnerability in the code handling the reassembly of fragmented IP version 4 (IPv4) or IP version 6 (IPv6) packets of Cisco IOS XE Software for Cisco ASR 1000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause a crash of the Embedded Services Processor (ESP) processing the packet," Cisco says in an advisory.
"The vulnerability is due to improper processing of crafted, fragmented packets.
"An attacker could exploit this vulnerability by sending a crafted sequence of fragmented packets [which] could allow the attacker to cause a reload of the affected platform."
Admins have no choice other than to patch the hole, rated a severity score of 7.8 for its its ease of attack, since fix workarounds are not known to exist.
Attackers will need to target the router directly as regular transit malformed packets will not trigger a crash.
System admins should update their vulnerable 2.3 and earlier IOS XE software versions to 2.5.1 or higher. Those running 2.4 or 2.5 should also update for other unstated reasons. ®