[ GLSA 200710-14 ] DenyHosts: Denial of Service

[GLSA]

Gentoo Linux Security Advisory

Title: DenyHosts: Denial of Service (GLSA 200710-14)
Severity: normal
Exploitable: remote
Date: October 13, 2007
Bug(s): #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: app-admin/denyhosts
Vulnerable: < 2.6-r1
Unaffected: >= 2.6-r1
Architectures: 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: