DNSSEC Validation Bypass via Out-of-Zone NSEC Next Field

Excessive NSEC3 iterations cause high CPU load during insecure delegation validation

Invalid handling of CLASS != IN

If a provably insecure domain is covered by both an NSEC and NSEC3 record at the parent, and there exist an RRSIG for only one of these types, then BIND may exit unexpectedly with an assertion while validating this proof. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.

An attacker's zone can respond with an RRSIG with fewer labels than the zone it's in, causing named to produce a wildcard name shorter than the attacker's zone — resulting in cache poisoning. Requires synth-from-dnssec yes (which IS the default).

"deny-answer-aliases" is a little-used feature intended to help recursive server operators protect end users against DNS rebinding attacks, a potential method of circumventing the security model used by client browsers. However, a defect in this feature makes it easy, when the feature is in use, to experience an assertion failure in name.c. Affects BIND 9.7.0->9.8.8, 9.9.0->9.9.13, 9.10.0->9.10.8, 9.11.0->9.11.4, 9.12.0->9.12.2, 9.13.0->9.13.2.

An attacker who is able to send and receive messages to an authoritative DNS server and who has knowledge of a valid TSIG key name for the zone and service being targeted may be able to manipulate BIND into accepting an unauthorized dynamic update. A server that relies solely on TSIG or SIG(0) keys with no other address-based ACL protection could be vulnerable to malicious zone content manipulation using this technique.

Workarounds:

The effects of this vulnerability can be mitigated by using Access Control Lists (ACLs) that require both address range validation and use of TSIG authentication in parallel. For information on how to configure this type of compound authentication control, please see:

https://kb.isc.org/article/AA-00723/0/Using-Access-Control-Lists-ACLs-with-both-addresses-and-keys.html.

Administrators who have made use of named.conf option "update-policy local;" should refer to the Administrator Reference Manual (ARM) for details of the automatic update policy that will be established and to assess whether or not this conveys any additional risk to their server. (Note that this option is not enabled by default).

Upstream patch:

https://source.isc.org/cgi-bin/gitweb.cgi?p=bind9.git;a=commitdiff;h=581c1526ab

Under some conditions when using both DNS64 and RPZ to rewrite query responses, query processing can resume in an inconsistent state leading to either an INSIST assertion failure or an attempt to read through a NULL pointer. Affects BIND 9.8.8, 9.9.3-S1 -> 9.9.9-S7, 9.9.3 -> 9.9.9-P5, 9.9.10b1, 9.10.0 -> 9.10.4-P5, 9.10.5b1, 9.11.0 -> 9.11.0-P2, 9.11.1b1.

Every named instance configured to run as a recursive resolver maintains a cache database holding the responses to the queries it has recently sent to authoritative servers. The size limit for that cache database can be configured using the max-cache-size statement in the configuration file; it defaults to 90% of the total amount of memory available on the host. When the size of the cache reaches 7/8 of the configured limit, a cache-cleaning algorithm starts to remove expired and/or least-recently used RRsets from the cache, to keep memory use below the configured limit. It has been discovered that the effectiveness of the cache-cleaning algorithm used in named can be severely diminished by querying the resolver for specific RRsets in a certain order, effectively allowing the configured max-cache-size limit to be significantly exceeded. This issue affects BIND 9 versions 9.11.0 through 9.16.41, 9.18.0 through 9.18.15, 9.19.0 through 9.19.13, 9.11.3-S1 through 9.16.41-S1, and 9.18.11-S1 through 9.18.15-S1.

A cache poisoning vulnerability was found in BIND when using forwarders. Bogus NS records supplied by the forwarders may be cached and used by name if it needs to recurse for any reason. This issue causes it to obtain and pass on potentially incorrect answers. This flaw allows a remote high privileged attacker to manipulate cache results with incorrect records, leading to queries made to the wrong servers, possibly resulting in false information received on the client's end.

named contains a feature which allows operators to issue commands to a running server by communicating with the server process over a control channel, using a utility program such as rndc. A regression introduced in a recent feature change has created a situation under which some versions of named can be caused to exit with a REQUIRE assertion failure if they are sent a null command string. Affects BIND 9.9.9->9.9.9-P7, 9.9.10b1->9.9.10rc2, 9.10.4->9.10.4-P7, 9.10.5b1->9.10.5rc2, 9.11.0->9.11.0-P4, 9.11.1b1->9.11.1rc2, 9.9.9-S1->9.9.9-S9.

BIND resolvers are vulnerable to an amplified resource consumption/exhaustion attack. If a victim resolver makes a query to a specially crafted zone, the resolver will consume disproportionate resources. This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

An attacker able to send and receive messages to an authoritative DNS server may be able to circumvent TSIG authentication of AXFR requests via a carefully constructed request packet. A server that relies solely on TSIG keys for protection with no other ACL protection could be manipulated into:

providing an AXFR of a zone to an unauthorized recipient accepting bogus Notify packets

An unauthorized AXFR (full zone transfer) permits an attacker to view the entire contents of a zone. Protection of zone contents is often a commercial or business requirement.

If accepted, a Notify sets the zone refresh interval to 'now'. If there is not already a refresh cycle in progress then named will initiate one by asking for the SOA RR from its list of masters. If there is already a refresh cycle in progress, then named will queue the new refresh request. If there is already a queued refresh request, the new Notify will be discarded. Bogus notifications can't be used to force a zone transfer from a malicious server, but could trigger a high rate of zone refresh cycles.

Workarounds:

The effects of this vulnerability can be mitigated by using Access Control Lists (ACLs) that require both address range validation and use of TSIG authentication in parallel. For information on how to configure this type of compound authentication control, please see:

https://kb.isc.org/article/AA-00723/0/Using-Access-Control-Lists-ACLs-with-both-addresses-and-keys.html.

(Note that this technique will not be effective against bogus Notify packets if an attacker is able to reach the target DNS server whilst using a spoofed sending address).

Upstream patch:

https://source.isc.org/cgi-bin/gitweb.cgi?p=bind9.git;a=commitdiff;h=581c1526ab

"managed-keys" is a feature which allows a BIND resolver to automatically maintain the keys used by trust anchors which operators configure for use in DNSSEC validation. Due to an error in the managed-keys feature it is possible for a BIND server which uses managed-keys to exit due to an assertion failure if, during key rollover, a trust anchor's keys are replaced with keys which use an unsupported algorithm. Versions affected: BIND 9.9.0 -> 9.10.8-P1, 9.11.0 -> 9.11.5-P1, 9.12.0 -> 9.12.3-P1, and versions 9.9.3-S1 -> 9.11.5-S3 of BIND 9 Supported Preview Edition. Versions 9.13.0 -> 9.13.6 of the 9.13 development branch are also affected. Versions prior to BIND 9.9.0 have not been evaluated for vulnerability to CVE-2018-5745.