OpenSSH: Denial of Service

1. Gentoo Linux Security Advisory

Advisory Reference	GLSA 200609-17 / openssh
Release Date	September 27, 2006
Latest Revision	September 27, 2006: 02
Impact	normal
Exploitable	remote

Package	Vulnerable versions	Unaffected versions	Architecture(s)
net-misc/openssh	< 4.3_p2-r5	>= 4.3_p2-r5	All supported architectures

Related bugreports: #148228

Synopsis

A flaw in the OpenSSH daemon allows remote unauthenticated attackers to cause a Denial of Service.

2. Impact Information

Background

OpenSSH is a free suite of applications for the SSH protocol, developed and maintained by the OpenBSD project.

Description

Tavis Ormandy of the Google Security Team discovered a Denial of Service vulnerability in the SSH protocol version 1 CRC compensation attack detector.

Impact

A remote unauthenticated attacker may be able to trigger excessive CPU usage by sending a pathological SSH message, denying service to other legitimate users or processes.

3. Resolution Information

Workaround

The system administrator may disable SSH protocol version 1 in /etc/ssh/sshd_config.

Resolution

All OpenSSH users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=net-misc/openssh-4.3_p2-r5"

4. References

CVE-2006-4924

Page updated September 27, 2006

Summary: This is a Gentoo Linux Security Advisory

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