CVE-2018-5738medium
Some versions of BIND can improperly permit recursive query service to unauthorized clients
18Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.3epss 11%
exploitation probability
11%top 4% of all CVEs
observed exploitation
nono source reports it
In short
BIND DNS servers can accidentally allow any client on the internet to perform recursive queries when they should only allow specific trusted clients. This happens due to a configuration bug introduced in late 2017, potentially exposing the server to abuse and attacks.
Technical detail
A regression in BIND's configuration parsing causes the 'allow-recursion' setting to incorrectly inherit permissive defaults from 'allow-query' when no explicit match lists are configured, allowing unauthorized recursive queries from all hosts. The vulnerability affects BIND versions 9.9.12, 9.10.7, 9.11.x, 9.12.0-P2, and 9.13.0 when recursion is enabled and allow-query-cache/allow-query lack explicit values, resulting in DNS amplification and cache poisoning attack vectors.
Summary generated and translated by AI from the official description.
Change #4777 (introduced in October 2017) introduced an unforeseen issue in releases which were issued after that date, affecting which clients are permitted to make recursive queries to a BIND nameserver. The intended (and documented) behavior is that if an operator has not specified a value for the "allow-recursion" setting, it SHOULD default to one of the following: none, if "recursion no;" is set in named.conf; a value inherited from the "allow-query-cache" or "allow-query" settings IF "recursion yes;" (the default for that setting) AND match lists are explicitly set for "allow-query-cache" or "allow-query" (see the BIND9 Administrative Reference Manual section 6.2 for more details); or the intended default of "allow-recursion {localhost; localnets;};" if "recursion yes;" is in effect and no values are explicitly set for "allow-query-cache" or "allow-query". However, because of the regression introduced by change #4777, it is possible when "recursion yes;" is in effect and no match list values are provided for "allow-query-cache" or "allow-query" for the setting of "allow-recursion" to inherit a setting of all hosts from the "allow-query" setting default, improperly permitting recursion to all clients. Affects BIND 9.9.12, 9.10.7, 9.11.3, 9.12.0->9.12.1-P2, the development release 9.13.0, and also releases 9.9.12-S1, 9.10.7-S1, 9.11.3-S1, and 9.11.3-S2 from BIND 9 Supported Preview Edition.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N