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Date: Fri, 13 Jun 2014 15:42:52 +0200
From: Vasyl Kaigorodov <vkaigoro@...hat.com>
To: oss-security@...ts.openwall.com
Subject: CVE request: PowerDNS in default configuration is vulnerable to DoS
 attack

It was found [1] that in default configuration PowerDNS is allowed to
consume more file descriptors than is available for a default installation
of many Linux distributions.
Default configuration is: 2 threads / 2048 max-mthreads, which leads
to a theoretical FD consumption of 4096. Default FD limit on many
distributions is 1024.
This can potentially lead to the DoS attack.

Workaround (from [1]):

- Reduce max-mthreads to 512 (or threads to 1 and max-mthreads to
1024) (max-mthreads was introduced in Recursor 3.2; but if you are
running a version that old, please upgrade it!)
- Run ‘ulimit -n 32768′ before starting (perhaps put this in
/etc/init.d/ script). There’s little reason to skip on this number.
- Investigate defaults in /etc/security/limits.conf

Patch is available at [2]

[1]: http://blog.powerdns.com/2014/02/06/related-to-recent-dos-attacks-recursor-configuration-file-guidance/
[2]: https://github.com/Habbie/pdns/commit/e24b124a4c7b49f38ff8bcf6926cd69077d16ad8

References:

https://bugs.mageia.org/show_bug.cgi?id=13521
https://bugzilla.redhat.com/show_bug.cgi?id=1109231

Can a CVE please be assigned if one has not been already?

Thanks.
-- 
Vasyl Kaigorodov | Red Hat Product Security Team
PGP:  0xABB6E828 A7E0 87FF 5AB5 48EB 47D0 2868 217B F9FC ABB6 E828

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