Florian Maury from ANSSI discovered that unbound, a validating, recursive, and caching DNS resolver, was prone to a denial of service vulnerability. An attacker crafting a malicious zone and able to emit (or make emit) queries to the server can trick the resolver into following an endless series of delegations, leading to resource exhaustion and huge network usage.

For the stable distribution (wheezy), this problem has been fixed in version 1.4.17-3+deb7u2. For the upcoming stable distribution (jessie), this problem has been fixed in version 1.4.22-3. For the unstable distribution (sid), this problem has been fixed in version 1.4.22-3. We recommend that you upgrade your unbound packages.

Unbound is a recursive-only caching DNS server which can perform DNSSEC validation of results. It implements only a minimal amount of authoritative service to prevent leakage to the root nameservers: forward lookups for localhost, reverse for 127.0.0.1 and ::1, and NXDOMAIN for zones served by AS112. Stub and forward zones are supported.

unbound on Debian Linux

This check tests the installed software version using the apt package manager.

• http://www.debian.org/security/2014/dsa-3097.html

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Updated on 2015-03-25