KPMG-2002030: Watchguard Firebox Dynamic VPN Configuration Protocol DoS

Type securityvulns
Reporter Securityvulns
Modified 2002-07-09T00:00:00


Title: Watchguard Firebox Dynamic VPN Configuration Protocol DoS

BUG-ID: 2002030 Released: 9th Jul 2002


A malicious user can crash the Dynamic VPN Configuration Protocol service (DVCP) by sending a malformed packet to the listener service on TCP port 4110.


  • Watchguard Firebox firmware v5.x.x

Not Vulnerable:

  • Watchguard Firebox firmware v6.0.b1140

Product Description:

Quoted from the vendor webpage:

"The WatchGuard® Firebox System is a powerful security solution that gives small and medium sized businesses, central offices, and VPN hubs integrated firewall protection and VPN support."

"About DVCP DVCP is a WatchGuard client server protocol that securely transmits IPSec VPN configuration information to WatchGuard Fireboxes. Network administrators use WatchGuard software to define each configuration aspect of the VPN, such as encryption algorithms and how often keys will be negotiated, then the settings are stored on a centrally located DVCP Server.When a Firebox is installed and initialized with software and instructions, a software client on the Firebox contacts the central DVCP server to obtain IPSec policy information using a secure protocol."


The DVCP service can be crashed using anywhere between 1 and 400 packets of tab characters, followed by a CRLF. The firewall needs to be rebooted for the DVCP service to function again.

Vendor URL:

You can visit the vendor webpage here:

Vendor response:

The vendor was notified on the 8th of May, 2002. On the 23rd of May, 2002 the vendor notified us that the issue would be resolved in the next version (6.x). On the 9th of July we verified that the problem was resolved in the new firmware version.

Corrective action:

Upgrade to firmware version 6.x, available at the livesecurity website. If you are not a subscriber to the livesecurity service, please contact Watchguard support further assistance.

Authors: Andreas Sandor ( Peter Gründl (

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