GLSA 200710-14: DenyHosts: Denial of Service

http://security.gentoo.org/

Severity:	normal
Title:	DenyHosts: Denial of Service
Date:	10/13/2007
Bugs:	#181213
ID:	200710-14

Synopsis

DenyHosts does not correctly parse log entries, potentially causing a remote Denial of Service.

Background

DenyHosts is designed to monitor SSH servers for repeated failed login attempts.

Affected packages

Package	Vulnerable	Unaffected	Architecture(s)
app-admin/denyhosts	< 2.6-r1	>= 2.6-r1	All supported architectures

Description

Daniel B. Cid discovered that DenyHosts used an incomplete regular expression to parse failed login attempts, a different issue than GLSA 200701-01.

Impact

A remote unauthenticated attacker can add arbitrary hosts into the blacklist, including the "all" keyword, by submitting specially crafted version identification strings to the SSH server banner. An attacker may use this to prevent legitimate users from accessing a host remotely.

Workaround

There is no known workaround at this time.

Resolution

All DenyHosts users should upgrade to the latest version:

    # emerge --sync
    # emerge --ask --oneshot --verbose ">=app-admin/denyhosts-2.6-r1"

References

CVE-2007-4323

Availability

This GLSA and any updates to it are available for viewing at the Gentoo Security Website: http://security.gentoo.org/glsa/glsa-200710-14.xml

Concerns?

Security is a primary focus of Gentoo Linux and ensuring the confidentiality and security of our users machines is of utmost importance to us. Any security concerns should be addressed to security@gentoo.org or alternatively, you may file a bug at https://bugs.gentoo.org.