Entering a long, invalid command to the terminal freezes the system

If I enter an invalid command that is a few thousand characters long it goes to the command-not-found program, and it starts to look for it in the repositories. This takes up a lot of RAM, and the whole system freezes.

By default, /usr/lib/command-not-found contains these lines:

    if len(args) == 1:
        cnf = CommandNotFound(options.data_dir)
        if not cnf.advise(args[0], options.ignore_installed) and not options.no_failure_msg:
            print(_("%s: command not found") % args[0], file=sys.stderr)

Adding a simple length check is enough to completely solve this problem.

    if len(args) == 1:
        # Fix crashing with long commands
        if len(args[0]) > 50:
            print(_("%s: command not found") % args[0], file=sys.stderr)
        else:
            cnf = CommandNotFound(options.data_dir)
            if not cnf.advise(args[0], options.ignore_installed) and not options.no_failure_msg:
                print(_("%s: command not found") % args[0], file=sys.stderr)

I'm having this issue in Ubuntu 14.04.04 with command-not-found 0.3ubuntu12, but the same code is in 16.10's packages.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: command-not-found 0.3ubuntu12 [modified: usr/lib/command-not-found]
ProcVersionSignature: Ubuntu 4.2.0-42.49~14.04.1-generic 4.2.8-ckt12
Uname: Linux 4.2.0-42-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.21
Architecture: amd64
CurrentDesktop: MATE
Date: Fri Jul 22 19:12:59 2016
PackageArchitecture: all
SourcePackage: command-not-found
UpgradeStatus: No upgrade log present (probably fresh install)