[ 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: