DenyHosts: Denial of Service — GLSA 200710-14

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

Affected Packages

app-admin/denyhosts on all architectures
Affected versions < 2.6-r1
Unaffected versions >= 2.6-r1

Background

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

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

Release Date
October 13, 2007

Latest Revision
October 13, 2007: 01

Severity
normal

Exploitable
remote

Bugzilla entries