FreeBSD: Local Privilege Escalation via Execve()

(freebsd.org)

56 points | by Deeg9rie9usi 2 hours ago

7 comments

  • cryptbe 1 hour ago
    Nice to randomly encounter our own work here.

    Check out our blog post for a fun walkthrough: https://blog.calif.io/p/cve-2026-7270-how-i-get-root-on-free...

    AI-generated working exploit, write-up and prompts: https://github.com/califio/publications/tree/main/MADBugs/fr...

  • tptacek 1 hour ago
    Calif is just killing it these past couple months. Reminder that Calif is Thai Duong's new firm.
    • cryptbe 58 minutes ago
      You're always super kind to me :)
  • cyberpunk 2 hours ago
    This is from April 28th, it was patched in 15.0R-p7.
    • itsthefrank 2 hours ago
      -p8 is the current patch level for 15.0-RELEASE so if people have been keeping on top of patching this is already two reboots in the past.
    • loeg 1 hour ago
      Just yesterday, cperciva was bragging about the FreeBSD approach to security: https://news.ycombinator.com/item?id=48056853 You can certainly argue the response here was well-coordinated, but having an LPE in a nearly 50-year old core syscall like execve() isn't ideal from a security perspective. (That is: security response isn't the entire picture; culture and bug surface matter too.)
      • broken-kebab 1 hour ago
        Or in other words, the response is well-coordinated so cperciva's bragging is justified, isn't it?
        • cperciva 24 minutes ago
          Indeed, I was thinking about this precise issue when I made the point that corresponding issues get handled much better in FreeBSD than in Linux.
      • yjftsjthsd-h 1 hour ago
        I think cperciva may have been a touch overenthusiastic, but surely this is in fact proving his point? His claim was, as you note before trying to ignore it, about coordination. When one of the recent Linux LPEs broke, the fix wasn't in distro packages yet; there was a vulnerability that users couldn't practically do anything about. This is an LPE that is fixed in the binaries that have already shipped. If I was playing cheerleader, this is exactly the case I'd use to argue that FreeBSD being a single unified system is a win and that its approach to handing security problems is very on top of things.
      • tptacek 1 hour ago
        He was talking about managing disclosure and patch flow, and you're just taking it as an opportunity to dunk on him.
      • bch 1 hour ago
        Its like rain on your wedding day - not actually ironic, just unfortunate.
      • stackghost 1 hour ago
        A not-insignificant chunk of the userbase of the various BSDs is there because they were turned off of Linux after controversial things like Gnome 3, systemd being shoved down users' throats despite being a broken mess, wayland (though nobody was as arrogant about wayland as Poettering was about systemd), etc.

        All that to say, the BSD userbase as a sizeable subset that are there for countercultural reasons, rather than technical. These are the people who buy into, say, OpenBSD's vaunted security reputation, or believe that "linux bad because reasons", so you're always going to get people in here bragging, because "not using linux" has become part of their identity.

        I run a mix of FreeBSD and Linux on my personal devices. The ground truth is that FreeBSD is yet another unix-like OS written in C, and thus not immune from the types of bugs that stem from that lineage. None of the BSD distros are materially more secure or better than a properly-configured and patched Linux.

        • applfanboysbgon 1 hour ago
          The person 'bragging' was not a countercultural user, but rather the FreeBSD engineering lead. They were, however, talking about FreeBSD's response to security vulnerabilities, in contrast to Linux's response.

          > thus not immune from the types of bugs that stem from that lineage

          They never claimed that FreeBSD didn't have vulnerabilities. I honestly have no idea why grandparent decided to bring up their comment when it exactly validates what the person they were criticising says. GP admits the response to the vulnerability was well-coordinated. The response to security vulnerabilities was the exact, and only, subject of the post they're calling out.

        • wolvoleo 1 hour ago
          I wouldn't call it countercultural. And Wayland actually runs on freebsd these days.

          I use Linux as well but I really like FreeBSD for a number of technical reasons. Like the ports collection, the jails, the first-class citizen ZFS.

          And Gnome 3 doesn't really have anything to do with Linux. It is also available for FreeBSD if you want it (I don't, I hate the minimalist opinionated design style so I use KDE, also on Linux).

          But I use Linux on servers where I run docker for example. It's not about "not using linux".

        • icedchai 1 hour ago
          I also use a mix. I moved to FreeBSD initially after a rough period w/Linux in the late 90's. Today, my FreeBSD machines are all VMs running on Linux hosts!
          • cyberpunk 1 hour ago
            Hah I'm your mirror version -- my linux machines are all VMs running on FreeBSD hosts!
            • wolvoleo 1 hour ago
              Oh you use bhyve?

              I've tried to use it but I dound it pretty difficult for systems that need a GUI. Maybe I should revisit.

              • cyberpunk 54 minutes ago
                Yep, most of my linuxes are headless -- but I do have a VM which I pass a graphics card through to for games and ai stuff though -- works really well (as long as you don't reboot the VM, it has a hard time attaching to the gfx card the second time for some reason, not looked into it much)

                sysutils/vm-bhyve makes it quite friendly.

                I wouldn't use it for work, though, just personal. Work is all enterprisey kubernetes stuff.

                Edit: there is a 'proxmox-like' for FreeBSD out [0] -- I did try it on a couple machines and couldn't get the network working, but consoles seemed to work.. Kinda.

                0: https://sylve.io

                • wolvoleo 49 minutes ago
                  Ah I don't really have a second GPU to dedicate to it though. A virtual console like in VMware or QEMU/KVM would be great. Thanks for the heads-up about sylve! I'll check it out.

                  For me it's all personal too. For work we still use VMWare a lot.

  • wolvoleo 1 hour ago
    Oof that's a pretty big one, I didn't realise but I had already updated anyway.
  • rvz 2 hours ago
    > IV. Workaround

    > No workaround is available.

    Oh dear.

    • itsthefrank 2 hours ago
      > V. Solution

      > Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date, and reboot the system.

      Not everyone can just freebsd-update and reboot, so yes, "Oh dear." is a good response to this.

      • epcoa 2 hours ago
        Anyone relying on a 30+ year old monolith kernel written in C to not have some exploitable LPEs lurking should stay in basket weaving and out of sysadmin.
        • itsthefrank 2 hours ago
          Not sure why the snark but if people are running FreeBSD then they should be...basket weaving instead of using it? Yes, the correct solution is to patch and reboot but not everyone is in a place to jump and do that which is why a temp workaround, if possible, would be welcome
          • wswin 1 hour ago
            I think good system should be prepared to do a reboot in a short notice. Even some long running jobs can have a pause mechanism.
        • cyberpunk 2 hours ago
          Yep.

          You should treat any system where non-admins regularly login as basically insecure/owned and rig your architecture appropriately.

          TBH -- I don't have any of these kinds of boxes anymore. Who is really running anything like this in 2026 and for what purpose?

          • mrln 1 hour ago
            Not necessarily FreeBSD, but for Linux this applies to most universities with a CS program, I think.

            The systems should be cut off from sensitive administrative data, but a malicious student would at the very least have access to the other students' data with an LPE.

          • bch 1 hour ago
            >> monolith kernel written in C

            > Who is really running anything like this in 2026 and for what purpose?

            Am I parsing your question correctly?

            • cyberpunk 1 hour ago
              No, I worded it badly. See below.
          • jmspring 1 hour ago
            Stability of ecosystem. No systemd. Native ZFS. Jails over Docker. Been using it for 20+ years and it’s my preferred server OS.
            • cyberpunk 1 hour ago
              No, I mean do you run FreeBSD boxes where users who should not ever assume root access actually login to do tasks?

              My point is that if you do, you probably shouldn't run, for e.g applications which need production db credential, or hold sensitive data on these boxes, or .. whatever.

              Edit: I use FreeBSD extensively, for various things -- but shell access to them is restricted to the sysadmins..

            • icedchai 1 hour ago
              Same. I've been using it since 1996. Initially, we used it at an early ISP for DNS, SMTP, and POP3 for roughly 8K users, and it stuck with me.
        • yjftsjthsd-h 1 hour ago
          ...as opposed to what, exactly? Linux is a 34 y.o. monolithic kernel in C, the BSDs are all forked from the same base (386BSD) of around the same age, XNU is 29 years old (and also heavily based on BSD code while also throwing in mach code) in C and other languages,...
      • skydhash 2 hours ago
        Why can't they? Upgrading and rebooting is kinda the standard response for most security issues. So I would expect something like Ansible's playbooks for this exact scenario. You might also have it setup as a staggered rollout.
      • paulddraper 1 hour ago
        What prevents it?
    • tptacek 1 hour ago
      Does this vulnerability not rely on SUID binaries?
      • cperciva 27 minutes ago
        I don't think so? It's a buffer overflow in the system call.
    • wolvoleo 1 hour ago
      Why? Just update.
  • doublerabbit 2 hours ago
    Linux is on their second and FreeBSD is on their first. How many is Windows on?
    • dwattttt 2 hours ago
      If you think Linux is on their first or second, I'm not sure how or what you're counting.
      • doublerabbit 1 hour ago
        > I'm not sure how or what you're counting.

        The recent two. FailCopy and DirtyFrag and FreeBSD with Execve.

        2 - Linux 1 - FreeBSD.

        Of course, all OS have had past-time exploits. Three now have made the news.

    • pjmlp 2 hours ago
      Plenty, Microsoft has security teams whose job is to attack Windows.

      Naturally they don't do blog posts about what they find.

      • murderfs 1 hour ago
        Local privilege escalation is largely irrelevant on Windows because basically no one uses it in a multi-user system, and application sandboxing is effectively nonexistent.
      • hnlmorg 1 hour ago
        You talk as if Windows is the only OS that has red teams attacking the system when clearly that isn’t even remotely true.
        • asveikau 13 minutes ago
          No, they're saying security work happens in the Windows world but not as much in the open, due to the closed source nature.