Joined: 12 May 2004
|Posted: Sat Oct 13, 2007 1:26 pm Post subject: [ GLSA 200710-14 ] DenyHosts: Denial of Service
|Gentoo Linux Security Advisory
Title: DenyHosts: Denial of Service (GLSA 200710-14)
Date: October 13, 2007
DenyHosts does not correctly parse log entries, potentially causing a remote Denial of Service.
DenyHosts is designed to monitor SSH servers for repeated failed login attempts.
Vulnerable: < 2.6-r1
Unaffected: >= 2.6-r1
Architectures: All supported architectures
Daniel B. Cid discovered that DenyHosts used an incomplete regular expression to parse failed login attempts, a different issue than GLSA 200701-01.
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.
There is no known workaround at this time.
All DenyHosts users should upgrade to the latest version:
|# emerge --sync
# emerge --ask --oneshot --verbose ">=app-admin/denyhosts-2.6-r1"