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Vulnerability of Squid: denial of service via FTP

Synthesis of the vulnerability 

A malicious FTP server can interrupt a session, in order to stop Squid.
Impacted software: Squid.
Severity of this computer vulnerability: 2/4.
Creation date: 05/12/2011.
Références of this announce: 3432, VIGILANCE-VUL-11194.

Description of the vulnerability 

The Squid proxy implements a web and FTP proxy.

The FTP protocol uses queries (sent by Squid) and replies (sent by the FTP server). When the FTP server interrupts a data session and its associated command session, a timeout occurs in Squid. At the end of this timeout, the errorDump() function of the src/errorpage.cc file is called to display an error message to the Squid client, which indicates the received reply. However, as the server interrupted its session, there is no reply, and the errorDump() function dereferences a NULL pointer.

A malicious FTP server can therefore interrupt a session, in order to stop Squid.
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This security alert impacts software or systems such as Squid.

Our Vigil@nce team determined that the severity of this security weakness is medium.

The trust level is of type confirmed by the editor, with an origin of internet server.

An attacker with a expert ability can exploit this security announce.

Solutions for this threat 

Squid: version 3.1.17.
The version 3.1.17 is corrected:
  http://www.squid-cache.org/Versions/v3/3.1/
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