title: DNS forwarders - cache poisoning vulnerability
description: BIND 9.11.0 -> 9.11.36 9.12.0 -> 9.16.26 9.17.0 -> 9.18.0 BIND Supported Preview Editions: 9.11.4-S1 -> 9.11.36-S1 9.16.8-S1 -> 9.16.26-S1 Versions of BIND 9 earlier than those shown - back to 9.1.0, including Supported Preview Editions - are also believed to be affected but have not been tested as they are EOL. The cache could become poisoned with incorrect records leading to queries being made to the wrong servers, which might also result in false information being returned to clients.
problem types: When using forwarders, bogus NS records supplied by, or via, those forwarders may be cached and used by named if it needs to recurse for any reason, causing it to obtain and pass on potentially incorrect answers. Some examples of configurations that will be vulnerable are:     Resolvers using per zone or global forwarding with forward first (forward first is the default).     Resolvers not using global forwarding, but with per-zone forwarding with either forward first (the default) or forward only.     Resolvers configured with global forwarding along with zone statements that disable forwarding for part of the DNS namespace. Authoritative-only BIND 9 servers are not vulnerable to this flaw. BIND     9.11.0 -> 9.11.36     9.12.0 -> 9.16.26     9.17.0 -> 9.18.0 BIND Supported Preview Editions:     9.11.4-S1 -> 9.11.36-S1     9.16.8-S1 -> 9.16.26-S1 Versions of BIND 9 earlier than those shown - back to 9.1.0, including Supported Preview Editions - are also believed to be affected but have not been tested as they are EOL.
affected:
{
vendor: ISC
product: BIND
versions:
version: Open Source Branch 9.11  9.11.0 through versions before 9.11.37, status: affected
version: Development Branch 9.17  BIND 9.17 all version, status: affected
version: Open Source Branch 9.12-16  9.12.0 through versions before 9.16.27, status: affected
version: Open Source Branch 9.18 9.18.0, status: affected
version: Supported Preview Branch 9.11-S 9.11.0-S through versions before 9.11.37-S, status: affected
version: Supported Preview Branch 9.16-S  9.16.0-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:H/UI:N/S:C/C:N/I:H/A:N
attackVector: NETWORK
attackComplexity: LOW
privilegesRequired: HIGH
userInteraction: NONE
scope: CHANGED
confidentialityImpact: NONE
integrityImpact: HIGH
availabilityImpact: NONE
baseScore: 6.8
baseSeverity: MEDIUM
]
solutions: Upgrade to the patched release most closely related to your current version of BIND:
BIND 9.11.37
BIND 9.16.27
BIND 9.18.1
BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.
BIND 9.11.37-S1
BIND 9.16.27-S1
workarounds: If applicable, modify your configuration to either remove all forwarding or all possibility of recursion. Depending on your use-case, it may be possible to use other zone types to replace forward zones.
Active exploits: We are not aware of any active exploits.