There’s been talk of this unauthenticated RCE vulnerability coming with a CVSS 9.9 rating but none of the technical details were publicly known until it was made public just now at the top of the hour. Simone Margaritelli discovered this vulnerability and has shared a write-up around this potentially very impactful Linux vulnerability.

This vulnerability, fortunately, doesn’t affect the Linux kernel but rather CUPS… The print server commonly used on Linux systems and other platforms.

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From Attacking UNIX Systems via CUPS, Part I:

“A remote unauthenticated attacker can silently replace existing printers’ (or install new ones) IPP urls with a malicious one, resulting in arbitrary command execution (on the computer) when a print job is started (from that computer).”

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This remote code execution issue can be exploited across the public Internet via a UDP packet to port 631 without needing any authentication, assuming the CUPS port is open through your router/firewall. LAN attacks are also possible via spoofing zeroconf / mDNS / DNS-SD advertisements.

Besides CUPS being used on Linux distributions, it also affects some BSDs, Oracle Solaris, Google Chrome OS, and others.

As of writing there is no Linux fix available for this high profile security issue. In the meantime it’s recommended to disable and remove the “cups-browsed” service, updating CUPS, or at least blocking all traffic to UDP port 631.

  • nyan@sh.itjust.works
    4·
    5 hours ago

    Yup, called it: non-mandatory piece of software. Plus you have to have been dumb enough to deliberately forward the port at your router for the general-case attack, and you have to print something (which I do maybe twice a month) for any command injection to take place.

    This does need to be patched, since there is some risk if you have CUPS running and another device on your LAN has already been compromised, but it’s definitely not the earthshattering kaboom the discoverer misrepresented it as.

    • Magiilaro@feddit.org
      1·
      43 minutes ago

      No port forwarding needed when the ISP provides a proper IPv6 subnet. Normal IPv6 router advertisement will then provide a public reachable address for every IPv6 capable device.

      But with the size of IPv6 it makes searching for that not really easy, so it only a small attack vector.

      • Laser@feddit.org
        1·
        3 minutes ago

        My router will still block all ports not explicitly allowed for the hosts regardless of protocol, it’s a firewall after all and not just NAT. Just because the host addressable doesn’t mean its ports are reachable.