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TUCoPS :: Linux :: Apps N-Z :: bt1724.txt

Quagga remote vulnerability


All versions of Quagga (and also GNU Zebra, from which Quagga was
forked) are vulnerable to a remotely triggerable denial of 

Scope of vulnerability:

All versions of GNU Zebra and all versions of Quagga /prior/ to
0.96.4, where a daemon's vty, ie the telnet CLI, is accessible to
hostile parties.


Affected daemons can be made to crash by sending a malformed telnet


The vty layer, when processing the telnet sub-negotiation ends
marker, SE, does not check whether there is sub-negotiation in
progress, and hence will attempt to dereference a (typically) NULL
pointer causing the daemon to crash.


Restrict access to daemon's telnet CLI, by either configuring each
daemon's vty with an appropriate access-class and access-list, or by
some external firewalling application.

Alternatively, disable external vty access completely by removing the 
vty password (and restarting) or passing the '-P 0' parameters to the 


Quagga version 0.96.4 contains a fix for this bug. Alternatively, one 
can manually apply the fix to whichever sources one uses currently. 
(See the RedHat bugzilla entry referenced below for the fix).


Thanks to Jonny Robertson <jonny AT> for finding
and reporting this bug and Jay Fenlason <fenlason AT> for 
fixing the bug.


RedHat Advisory RHSA-2003:307-09,

RedHat Bugzilla entry 107140,



The RedHat Advisory references a second vulnerability in GNU Zebra 
and Quagga, regarding the zebra daemon accepting netlink messages 
from any user. This vulnerability will be dealt with as soon as 

Paul Jakma	Key ID: 64A2FF6A
	warning: do not ever send email to
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