[ GLSA 200701-01 ] DenyHosts: Denial of Service

[GLSA]

Gentoo Linux Security Advisory

Title: DenyHosts: Denial of Service (GLSA 200701-01)
Severity: normal
Exploitable: remote
Date: January 03, 2007
Bug(s): #157163
ID: 200701-01

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: app-admin/denyhosts
Vulnerable: < 2.6
Unaffected: >= 2.6
Architectures: All supported architectures


Description


Tavis Ormandy of the Gentoo Linux Security Audit Team discovered that
DenyHosts used an incomplete regular expression to parse failed login
attempts.


Impact


A remote unauthenticated attacker can add arbitrary hosts to the
blacklist by attempting to login with a specially crafted username. 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: