pdnsd: Denial of Service and cache poisoning

Security Team Contact Address

Updated January 11, 2009

1. Gentoo Linux Security Advisory

Advisory Reference	GLSA 200901-03 / pdnsd
Release Date	January 11, 2009
Latest Revision	January 11, 2009: 01
Impact	normal
Exploitable	remote

Package	Vulnerable versions	Unaffected versions	Architecture(s)
net-dns/pdnsd	< 1.2.7	>= 1.2.7	All supported architectures

Related bugreports: #231285

Synopsis

Two errors in pdnsd allow for Denial of Service and cache poisoning.

2. Impact Information

Background

pdnsd is a proxy DNS server with permanent caching that is designed to cope with unreachable DNS servers.

Description

Two issues have been reported in pdnsd:

The p_exec_query() function in src/dns_query.c does not properly handle many entries in the answer section of a DNS reply, related to a "dangling pointer bug" (CVE-2008-4194).
The default value for query_port_start was set to 0, disabling UDP source port randomization for outgoing queries (CVE-2008-1447).

Impact

An attacker could exploit the second weakness to poison the cache of pdnsd and thus spoof DNS traffic, which could e.g. lead to the redirection of web or mail traffic to malicious sites. The first issue can be exploited by enticing pdnsd to send a query to a malicious DNS server, or using the port randomization weakness, and might lead to a Denial of Service.

3. Resolution Information

Workaround

Port randomization can be enabled by setting the "query_port_start" option to 1024 which would resolve the CVE-2008-1447 issue.

Resolution

All pdnsd users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=net-dns/pdnsd-1.2.7"

4. References