title: A stack exhaustion flaw in control channel code may cause named to terminate unexpectedly
description: The code that processes control channel messages sent to `named` calls certain functions recursively during packet parsing. Recursion depth is only limited by the maximum accepted packet size; depending on the environment, this may cause the packet-parsing code to run out of available stack memory, causing `named` to terminate unexpectedly. Since each incoming control channel message is fully parsed before its contents are authenticated, exploiting this flaw does not require the attacker to hold a valid RNDC key; only network access to the control channel's configured TCP port is necessary.
This issue affects BIND 9 versions 9.2.0 through 9.16.43, 9.18.0 through 9.18.18, 9.19.0 through 9.19.16, 9.9.3-S1 through 9.16.43-S1, and 9.18.0-S1 through 9.18.18-S1.
affected:
{
vendor: ISC
product: BIND 9
versions:
version: 9.2.0, lessThanOrEqual: 9.16.43, status: affected, versionType: custom
version: 9.18.0, lessThanOrEqual: 9.18.18, status: affected, versionType: custom
version: 9.19.0, lessThanOrEqual: 9.19.16, status: affected, versionType: custom
version: 9.9.3-S1, lessThanOrEqual: 9.16.43-S1, status: affected, versionType: custom
version: 9.18.0-S1, lessThanOrEqual: 9.18.18-S1, status: affected, versionType: custom
defaultStatus: unaffected
}
metrics:
cvssV3_1: [
version: 3.1
attackVector: NETWORK
attackComplexity: LOW
privilegesRequired: NONE
userInteraction: NONE
scope: UNCHANGED
confidentialityImpact: NONE
integrityImpact: NONE
availabilityImpact: HIGH
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
baseScore: 7.5
baseSeverity: HIGH
]
exploits: We are not aware of any active exploits.
solutions: Upgrade to the patched release most closely related to your current version of BIND 9: 9.16.44, 9.18.19, 9.19.17, 9.16.44-S1, or 9.18.19-S1.
workarounds: By default, `named` only allows control-channel connections over the loopback interface, making this attack impossible to carry out over the network. When enabling remote access to the control channel's configured TCP port, care should be taken to limit such access to trusted IP ranges on the network level, effectively preventing unauthorized parties from carrying out the attack described in this advisory.