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WebWasher Classic - HTTP CONNECT Weakness
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SUMMARY
<http://www.webwasher.com/> WebWasher Classic is "a well known
HTTP-URL/Popup/Script filtering proxy which is free for non commercial
use".
A flaw in the design of WebWasher allows a malicious attacker to bypass
firewall rules and ACLs and connect to the machine running WebWasher even
when not permitted.
DETAILS
Vulnerable Systems:
* WebWasher Classic v3.3 and v.2.2.1 on Windows platform.
WebWasher Classic supports two modes, a client mode, where it only works
for the local machine (bound to localhost) and a server mode, where it
serves as a network proxy (bound to 0.0.0.0).
When running in server mode, it is possible to connect from remote to tcp
ports listening on 127.0.0.1 of the WebWasher system. This is a design
flaw, because CONNECT requests to localhost should be denied. It also may
be possible to bypass ACL of firewalls that protect the WebWasher system.
Proof of Concept:
1) Start a netcat listener on the WebWasher system:
netcat -L -p 99 -s 127.0.0.1 < hallo.txt
2) Connect to the WebWasher proxy port (default 8080/tcp)
3) Enter command "CONNECT 127.0.0.1:99 HTTP/1.0"
4) As a result, content of hallo.txt will appear.
ADDITIONAL INFORMATION
The information has been provided by <mailto:Oliver.Karow@gmx.de> Oliver
Karow.
The original article can be found at:
<http://www.oliverkarow.de/research/WebWasherCONNECT.txt>
http://www.oliverkarow.de/research/WebWasherCONNECT.txt
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