Getting debug access on a Brother printer over Telnet

(inventor7777.github.io)

65 points | by inventor7777 2 days ago

10 comments

  • jordand 1 minute ago
    The article linked at the bottom of this is a much more interesting read: https://starlabs.sg/blog/2025/11-breaking-into-a-brother-mfc...
  • kalleboo 1 hour ago
    The interesting part to me in there is seeing a TRON kernel in the wild.

    In the 80's TRON was Japan's bet for the future of operating systems, but it just lived on as an embedded kernel in cars, printers and other industrial applications.

    https://en.wikipedia.org/wiki/TRON_project

    https://www.osnews.com/story/145872/japan-tried-to-build-an-...

  • MayeulC 29 minutes ago
    This is something I have been wondering for a while: do custom laser printer firmware projects exist? I'm mostly interested in that to remove toner manufacturer checks, and fix a few annoyances in CUPS and the printers' postscript drivers.

    I imagine that is shouldn't be too complicated to support more HW in the agentic age.

  • amstan 2 hours ago
    I can't tell if any of this gives you more access than the normal http admin interface.
    • cheschire 1 hour ago
      Well now you can point an LLM at it. I’m not sure that gives you anything either, but I’m not sure the hacker ethos makes that a priority.

      Sometimes a hack is just cool because it’s a hack.

    • dizhn 1 hour ago
      As far as I can tell, it doesn't. The web interface is like 90s website but it does have a million suboptions. None of these seem like it needed any hacking. I am not sure about the Debug ones. I'll have to check. I wouldn't be surprised if there was an available api listening with the same commands available. If not that would be the useful outcome from work like this. A CLI that implements these.

      Now if you could use to allow firmware downgrades when the installed firmware doesn't, that would be useful too. I disabled updates on mine at a version that already allows it. I bought it a few weeks ago but luckily it didn't come with the latest "I don't like your ink chip" firmware.

  • ciex 1 hour ago
    But what are the things you would want from a printer that is already quite reliable, not DRM'd, and presumably compatible with all the devices you want to use it with?
  • devy 3 hours ago
    Great write up and reverse engineering of firmware! I hope to see Epson MFC inkjet printers to have similar discovery too (perhaps it literally a prompt away with a link to this article).
    • gregoryl 2 hours ago
      I was digging around an epson receipt printers firmware recently; got as far as discovering http endpoints (hardcoded auth) to remotely enable ssh (but not login), and some other diagnostic access. They seem fairly well put together.
  • greyface- 2 hours ago
    The same SET USER 640184.571119 command works on my 2012 Brother MFC-9460CDN.
  • nubinetwork 2 hours ago
    But what do those numbers mean?
  • cellsstudio 2 hours ago
    This is a really cool little project. Also, the title gave me a strong hit of like mid 2000's internet "hacking" content that I tore through when I was in high school.
    • NitpickLawyer 2 hours ago
      The e-zines can make a comeback, there's probably enough content now. phreak2030s: "put the local load in the bearing firmwares". Or something :)
  • josteink 1 hour ago
    This piece had potential but IMO was a bit disappointing. The entire thing could be summarized as:

    1. "I used AI to download and analyze a firmware image, and found a way to unlock DEBUG mode."

    2. "I didn't actually explore the DEBUG mode at all, but here are the commands the AI found for me (link)"

    I'd love for the author to at least put in a little real effort, explore some of these debug commands, and tell us why they are interesting.

    As this is - I find it to be very minimum-effort, AI-assisted blog-slop. Sorry!

    (Now for the link[1] to the actual (unexplored) debug-commands... It has really weird casing of the descriptions in the "behaviour"-column. Does anyone know why that is?)

    [1] https://inventor7777.github.io/brother-mfc-commands-list.htm...

    • lmz 1 hour ago
      The weird casing seems to be a minimum accepted prefix for the keywords.