CVE-2016-6171

Severity: high (CVSS 8.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2017-02-09 · updated 2026-06-17
Weakness: CWE-400

Description

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.

Affected products

Knot-Dns Knot Dns: before 2.3.0 — fixed in 2.3.0

How to fix

Upgrade to a fixed version: Knot-Dns Knot Dns 2.3.0. Check the vendor advisory for mitigations.

References

http://www.openwall.com/lists/oss-security/2016/07/06/3
http://www.openwall.com/lists/oss-security/2016/07/06/4
http://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
http://www.openwall.com/lists/oss-security/2016/07/06/3
http://www.openwall.com/lists/oss-security/2016/07/06/4
http://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

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