title: A malformed request can trigger an assertion failure in badcache.c
description: While handling a particular type of malformed packet BIND erroneously selects a SERVFAIL rcode instead of a FORMERR rcode. If the receiving view has the SERVFAIL cache feature enabled, this can trigger an assertion failure in badcache.c when the request doesn't contain all of the expected information. Affects BIND 9.10.5-S1 to 9.10.5-S4, 9.10.6-S1, 9.10.6-S2.
problem types: Servers running the affected versions (9.10.5-S1 to 9.10.5-S4, 9.10.6-S1, and 9.10.6-S2) are vulnerable if they allow recursion, unless the SERVFAIL cache is disabled for the receiving view.
affected:
{
product: BIND 9
vendor: ISC
versions:
status: affected, version: 9.10.5-S1 to 9.10.5-S4, 9.10.6-S1, 9.10.6-S2
}
metrics:
cvssV3_0: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 7.5
baseSeverity: HIGH
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
version: 3.0
]
solutions: Upgrade to the patched release.
No publicly released versions of BIND are affected
BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.
BIND 9 version 9.10.6-S3
workarounds: Disabling the SERVFAIL cache with 'servfail-ttl 0;' will prevent taking the code path that leads to the assertion failure.