title: DoS from specifically crafted TCP packets
description: BIND 9.16.11 -> 9.16.26, 9.17.0 -> 9.18.0 and versions 9.16.11-S1 -> 9.16.26-S1 of the BIND Supported Preview Edition. Specifically crafted TCP streams can cause connections to BIND to remain in CLOSE_WAIT status for an indefinite period of time, even after the client has terminated the connection.
problem types: ISC recently discovered an issue in BIND that allows TCP connection slots to be consumed for an indefinite time frame via a specifically crafted TCP stream sent from a client. This issue is present in BIND. BIND 9.16.11 -> 9.16.26, 9.17.0 -> 9.18.0 and versions 9.16.11-S1 -> 9.16.26-S1 of the BIND Supported Preview Edition. 9.16.11 to 9.16.26 (including S editions), and 9.18.0. This issue can only be triggered on BIND servers which have keep-response-order enabled, which is not the default configuration. The keep-response-order option is an ACL block; any hosts which are specified within it will be able to trigger this issue on affected versions. BIND 9.16.11 -> 9.16.26, 9.17.0 -> 9.18.0 and versions 9.16.11-S1 -> 9.16.26-S1 of the BIND Supported Preview Edition.
affected:
{
vendor: ISC
product: BIND
versions:
version: Open Source Branch 9.16 9.16.11 through versions before 9.16.27, status: affected
version: Development Branch 9.17 BIND 9.17 all versions, status: affected
version: Open Source Branch 9.18 9.18.0, status: affected
version: Supported Preview Branch 9.16-S 9.16.11-S through versions before 9.16.27-S, status: affected
}
metrics:
cvssV3_1: [
version: 3.1
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
attackVector: NETWORK
attackComplexity: LOW
privilegesRequired: NONE
userInteraction: NONE
scope: UNCHANGED
confidentialityImpact: NONE
integrityImpact: NONE
availabilityImpact: LOW
baseScore: 5.3
baseSeverity: MEDIUM
]
solutions: Upgrade to the patched release most closely related to your current version of BIND:
9.16.27
9.18.1
BIND Supported Preview Edition is a special feature-preview branch of BIND provided to eligible ISC support customers.
9.16.27-S1
workarounds: To mitigate this issue in all affected versions of BIND, use the default setting of keep-response-order { none; }.
Active exploits: We are not aware of any active exploits.