BIND 9 resolver can crash when stale cache and stale answers are enabled, option stale-answer-client-timeout is set to a positive integer, and the resolver receives an RRSIG query. This issue affects BIND 9 versions 9.16.12 through 9.16.36, 9.18.0 through 9.18.10, 9.19.0 through 9.19.8, and 9.16.12-S1 through 9.16.36-S1.
{
    "availability": "No subscription required",
    "binaries": [
        {
            "binary_name": "bind9",
            "binary_version": "1:9.18.1-1ubuntu1.3"
        },
        {
            "binary_name": "bind9-dev",
            "binary_version": "1:9.18.1-1ubuntu1.3"
        },
        {
            "binary_name": "bind9-dnsutils",
            "binary_version": "1:9.18.1-1ubuntu1.3"
        },
        {
            "binary_name": "bind9-host",
            "binary_version": "1:9.18.1-1ubuntu1.3"
        },
        {
            "binary_name": "bind9-libs",
            "binary_version": "1:9.18.1-1ubuntu1.3"
        },
        {
            "binary_name": "bind9-utils",
            "binary_version": "1:9.18.1-1ubuntu1.3"
        },
        {
            "binary_name": "bind9utils",
            "binary_version": "1:9.18.1-1ubuntu1.3"
        },
        {
            "binary_name": "dnsutils",
            "binary_version": "1:9.18.1-1ubuntu1.3"
        }
    ]
}