Knot Resolver before 5.1.1 allows traffic amplification via a crafted DNS answer from an attacker-controlled server, aka an "NXNSAttack" issue. This is triggered by random subdomains in the NSDNAME in NS records.
{
"binaries": [
{
"binary_version": "2.1.1-1ubuntu0.1~esm2",
"binary_name": "knot-resolver"
},
{
"binary_version": "2.1.1-1ubuntu0.1~esm2",
"binary_name": "knot-resolver-module-http"
},
{
"binary_version": "2.1.1-1ubuntu0.1~esm2",
"binary_name": "libkres-dev"
},
{
"binary_version": "2.1.1-1ubuntu0.1~esm2",
"binary_name": "libkres6"
}
]
}