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Vigil@nce: Checkpoint VPN-1, obtaining the private IP address

November 2008 by Vigil@nce


An attacker can obtain the private IP address of services with a PAT address translation.

Gravity: 1/4

Consequences: data reading

Provenance: intranet client

Means of attack: no proof of concept, no attack

Ability of attacker: expert (4/4)

Confidence: unique source (2/5)

Diffusion of the vulnerable configuration: high (3/3)

Creation date: 18/11/2008


- CheckPoint VPN-1


The Checkpoint VPN-1 firewall can be configured to translate some ports (PAT, Port Address Translation) to internal computers with a private IP address. The port 18264/tcp is typically configured with PAT to reach the Firewall Management Server.

The TTL field of an IP packet indicates the number of routers that a packet can cross. This number is decremented on each router. When it reaches zero, an ICMP error message is sent back to the source. This ICMP message contains the beginning of the failed packet.

However, when the TTL reaches zero on the firewall, the returned ICMP packet contains the private IP address instead of the IP address of the firewall.

An attacker can thus obtain the IP address of services translated with PAT.


Identifiers: BID-32306, VIGILANCE-VUL-8255

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