Schroot before 1.6.13 had too permissive rules on chroot or session names, allowing a denial of service on the schroot service for all users that may start a schroot session.
{
    "availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
    "binaries": [
        {
            "binary_name": "dchroot",
            "binary_version": "1.6.10-1ubuntu3+esm1"
        },
        {
            "binary_name": "dchroot-dsa",
            "binary_version": "1.6.10-1ubuntu3+esm1"
        },
        {
            "binary_name": "libsbuild-dev",
            "binary_version": "1.6.10-1ubuntu3+esm1"
        },
        {
            "binary_name": "schroot",
            "binary_version": "1.6.10-1ubuntu3+esm1"
        },
        {
            "binary_name": "schroot-common",
            "binary_version": "1.6.10-1ubuntu3+esm1"
        }
    ]
}