title: A broken inbound incremental zone update (IXFR) can cause named to terminate unexpectedly
description: In BIND 9.8.5 -> 9.8.8, 9.9.3 -> 9.11.29, 9.12.0 -> 9.16.13, and versions BIND 9.9.3-S1 -> 9.11.29-S1 and 9.16.8-S1 -> 9.16.13-S1 of BIND 9 Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.11 of the BIND 9.17 development branch, when a vulnerable version of named receives a malformed IXFR triggering the flaw described above, the named process will terminate due to a failed assertion the next time the transferred secondary zone is refreshed.
problem types: Incremental zone transfers (IXFR) provide a way of transferring changed portion(s) of a zone between servers. An IXFR stream containing SOA records with an owner name other than the transferred zone's apex may cause the receiving named server to inadvertently remove the SOA record for the zone in question from the zone database. This leads to an assertion failure when the next SOA refresh query for that zone is made.  Affects BIND 9.8.5 -> 9.8.8, 9.9.3 -> 9.11.29, 9.12.0 -> 9.16.13, and versions BIND 9.9.3-S1 -> 9.11.29-S1 and 9.16.8-S1 -> 9.16.13-S1 of BIND 9 Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.11 of the BIND 9.17 development branch.
affected:
{
product: BIND9
vendor: ISC
versions:
status: affected, version: Open Source Branch 9.8 9.8.5 through 9.8.8
status: affected, version: Open Source Branches 9.9 through 9.11 9.9.3 through versions before 9.11.30
status: affected, version: Open Source Branches 9.12 through 9.16 9.12.0 through versions before 9.16.14
status: affected, version: Supported Preview Branches 9.9-S through 9.11-S 9.9.3-S1 through versions before 9.11.30-S1
status: affected, version: Supported Preview Branch 9.16-S 9.16.8-S1 through versions before 9.16.14-S1
status: affected, version: Development Branch 9.17 9.17.0 through versiosn before 9.17.12
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 6.5
baseSeverity: MEDIUM
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: LOW
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
version: 3.1
]
exploits: We are not aware of any active exploits.
solutions: Upgrade to the patched release most closely related to your current version of BIND:
BIND 9.11.31
BIND 9.16.15
BIND 9.17.12
BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.
BIND 9.11.31-S1
BIND 9.16.15-S1
workarounds: Disabling incremental zone transfers (IXFR) by setting request-ixfr no; in the desired configuration block (options, zone, or server) prevents the failing assertion from being evaluated.