Squid: Denial of service when using NTLM authentication

1. Gentoo Linux Security Advisory

Advisory Reference	GLSA 200409-04 / squid
Release Date	September 02, 2004
Latest Revision	December 30, 2007: 03
Impact	normal
Exploitable	remote

Package	Vulnerable versions	Unaffected versions	Architecture(s)
net-proxy/squid	<= 2.5.6-r1	>= 2.5.6-r2, < 2.5	All supported architectures

Related bugreports: #61280

Synopsis

Squid is vulnerable to a denial of service attack which could crash its NTLM helpers.

2. Impact Information

Background

Squid is a full-featured Web Proxy Cache designed to run on Unix systems. It supports proxying and caching of HTTP, FTP, and other URLs, as well as SSL support, cache hierarchies, transparent caching, access control lists and many other features.

Description

Squid 2.5.x versions contain a bug in the functions ntlm_fetch_string() and ntlm_get_string() which lack checking the int32_t offset "o" for negative values.

Impact

A remote attacker could cause a denial of service situation by sending certain malformed NTLMSSP packets if NTLM authentication is enabled.

3. Resolution Information

Workaround

Disable NTLM authentication by removing any "auth_param ntlm program ..." directives from squid.conf or use ntlm_auth from Samba-3.x.

Resolution

All Squid users should upgrade to the latest stable version:

Code Listing 3.1: Resolution

# emerge sync

# emerge -pv ">=net-www/squid-2.5.6-r2"
# emerge ">=net-www/squid-2.5.6-r2"

4. References

Page updated September 02, 2004

Summary: This is a Gentoo Linux Security Advisory

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