FireWall-1 users feel the heat from security bug
Packet header headache
Security clearing house CERT has issued a security notice warning that the protection offered by a market leading firewall could be side stepped by determined crackers.
According to an advisory issued by CERT yesterday, a vulnerability in Check Point FireWall-1 (version 4.1) and VPN-1 may allow an intruder to pass traffic through the firewall on port 259/UDP by faking packet headers.
The bug permits a catalogue of exploits ranging from mounting denial of service attacks to permitting a cracker to communicate with a Trojan horse program planted on supposedly protected hosts to tunnelling arbitrary traffic across a firewall boundary.
On the face of it this sounds very unpleasant, but Deri Jones of security testing specialist NTA Monitor said that in practice the worst aspect of the bug is that it allows hackers to communicate with Trojan horse programs.
"Port 259/UDP is a pretty wacky port and hackers would be lucky to find machines listening on that port so the risk from denial of service attacks is low," said Jones.
The flaw, which was discovered by German security consultancy Inside Security, arises from default management rules employed by Check Point which allow arbitrary RDP (Reliable Data Protocol) connections to traverse the firewall.
RDP (UDP/259) is a proprietary protocol used by Check Point for internal communication between software components and is enabled by default to simplify encryption set-up. It is not the same as IP protocol 27.
Researchers at Inside Security have discovered a lack of controls applied to the protocol which means "by adding a faked RDP header to normal UDP traffic any content can be passed to port 259 on any remote host on either side of the firewall".
Inside Security has produced proof of concept code to prove that the exploit is possible, which it said it would release in a few days.
Check Point has produced a patch to address the issue, which it recommends all affected sites should apply as soon as possible. CERT advises users to block access to port 259/UDP until the patch is applied.
NTA Monitor's Jones said even though FireWall-1 is a "pretty stable" and well respected product security issues with the software arise from time to time, and need to be treated seriously given the product is central to the security infrastructure of many firms. ®