#VU39670 Resource exhaustion in Knot DNS - CVE-2016-6171

Vulnerability identifier: #VU39670

Vulnerability risk: High

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]

CVE-ID: CVE-2016-6171

CWE-ID: CWE-400

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Knot DNS
Server applications / DNS servers

Vendor: Nic

Description

The vulnerability allows a remote non-authenticated attacker to a crash the entire system.

Knot DNS before 2.3.0 allows remote DNS servers to cause a denial of service (memory exhaustion and slave server crash) via a large zone transfer for (1) DDNS, (2) AXFR, or (3) IXFR.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Knot DNS: 2.0.0 - 2.2.1

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External links
https://www.openwall.com/lists/oss-security/2016/07/06/3
https://www.openwall.com/lists/oss-security/2016/07/06/4
https://www.securityfocus.com/bid/91678
https://github.com/sischkg/xfer-limit/blob/master/README.md
https://gitlab.labs.nic.cz/labs/knot/blob/c546a70563ef4c7badb7cb5bdf6d1ba8e7adae82/NEWS
https://gitlab.labs.nic.cz/labs/knot/issues/464
https://lists.dns-oarc.net/pipermail/dns-operations/2016-July/015058.html

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.