Juniper's M- and T-Series routers are affected by the vulnerability in Junos 6.x, which makes them vulnerable to denial-of service attacks. Such an attack could allow a hacker to gain access to the router and crucial areas of the network.
Juniper confirmed the existence of the flaw on Monday.
"It is being fixed in that our customers are upgrading, but I'm not able to give any more details," said Penny Still, a spokeswoman for Juniper.
According to vulnerability researcher Secunia, the vulnerability has "moderately critical" implications for networks. In a Web site advisory, Secunia said that the vulnerability was caused by an unspecified error in processing certain network packets. It recommended that people upgrade the operating systems on their routers.
The vulnerability is thought to affect routers running versions of Junos installed before 7 January 2005. It was discovered by US-based company Qwest.
ZDNet UK's Dan Ilett reported from London. For more coverage from ZDNet UK, click here.
