Government Rails Site Hit Hours After CVE Patch

Government Rails Site Hit Hours After CVE Patch(rietta.com)

103 points by rietta 18 hours ago | 32 comments

Just sent this to my boss. Felt like tossing a grenade over a fence into a party of unsuspecting people.

We don’t use ActiveStorage but Claude was able create a similar exploit in own our app in the exact same way via our own file upload library in 3 minutes simply by point Opus 5 at our site and asking it if we were vulnerable to an attack similar to KindaRails2Shell.

What a time to be alive.

jcupitt 4 hours ago | |

The fix is pretty easy -- you should call `block_untrusted` to stop loaders like matlab from running:

https://www.rubydoc.info/gems/ruby-vips/Vips.block_untrusted

You can also set the env var `VIPS_BLOCK_UNTRUSTED`, which might be easier.

You can block or allow specific load operations, so you can limit format support to just the types you need:

https://www.rubydoc.info/gems/ruby-vips/Vips#block-class_met...

That might be even better.

There was a post on libvips.org about this a while ago:

https://www.libvips.org/2022/05/28/What's-new-in-8.13.html

And a note about it in the checklist for devs:

https://www.libvips.org/API/current/developer-checklist.html...

tyre 16 hours ago |

This post could be 10% as long:

- There was a bug with a patch

- We applied it to our clients

- There were live exploits within eight hours of the patch being released

- The Rails team had to expedite release of the technical details because POCs obviated the need to embargo

adastra22 5 hours ago | |

What is shocking to me is that it took eight hours.

comrade1234 18 hours ago |

Do you have to have matlab running on your rails server for this to happen?

bradly 17 hours ago | |

Not running, but supported. You can check your app with:

    bin/rails runner '
      require "vips"
      puts "ruby-vips #{Vips::VERSION}  libvips #{Vips.version(0)}.#{Vips.version(1)}.#{Vips.version(2)}"
      begin
        Vips::Operation.new("matload")
        puts "matload PRESENT - this build can reach libmatio"
      rescue Vips::Error
        puts "matload ABSENT - this build cannot reach libmatio"
      end
    '

This is from the Rails official docs for the CVE which, interestingly, they only released as an agent skill. https://github.com/rails/rails-forensics-CVE-2026-66066/blob...

XenoCyber0 12 hours ago | | |

An agent skill is the official distribution format for the forensics on a 9.5. I mean, I get it, anyone running a Rails app right now is pasting "am I affected" into an agent anyway, but it's the kind of thing that would've sounded like a joke a couple years ago.

comrade1234 13 hours ago | | |

Why would you have matlab on an external server? People don't even have a compiler on the server in this situation. Crazy.

fishtoaster 17 hours ago | |

I think the answer is no - this would affect any Rails app with default settings that uses ActiveStorage. The "Preconditions" recap at the bottom here has all the appropriate caveats: https://ethiack.com/info-hub/research/kindarails2shell-how-a...

rietta 17 hours ago | |

I am not sure, but my read on the original disclosure is no. libvips itself has a variant processor for matlab v5 files, which the exploit took advantage of.

kawsper 17 hours ago | | |

libvips also have a block_untrusted mode where it will block unsafe loaders, .mat seems to be marked as untrusted:

    vips -l
    VipsForeignLoadMat (matload), load mat from file (.mat), priority=0, untrusted, is_a, get_flags, get_flags_filename, header, load

jeremyjh 13 hours ago |

Nice write up, Claude.

onemoresoop 11 hours ago |

This website is format is really weird for mobile, I can only read two lines of text. The rest is covered by a big banner. Im on IOS. Anybody else having this issue or is it just me?

rietta 11 hours ago | |

Thanks for the heads up. The navigation header does not collapse as I never liked hamburger menus but it should be more than two lines. Works more than that on my iPhone 16. What size is yours? I will pull it up in the Firefox simulator next week and try to make it better.

We recently updated the design. This is a very old site so it has some quirks in the design for sure.

bavell 10 hours ago | | |

Android Firefox here, top nav takes up 1/3rd of the viewport

dorianmariecom 18 hours ago |

i thought cloudflare would protect against those no?

bastawhiz 12 hours ago | |

Since the vulnerability is exploited by a crafted binary file, I think that isn't something that CF's managed ruleset is able to protect against. They have the ability to scan incoming files with antivirus, but if the exploit is small and simple and can be mutated per request, I think it's unlikely any AV would pick it up.

rietta 12 hours ago | | |

I agree. And unstated in this write up is the direct upload route. Even if your Cloudflare was perfect, once the attacker got the preflight they send the binary file up to S3 directly and then hit the variant route directly. The first code to “validate” the upload was the exploitable libvips code.

rietta 17 hours ago | |

Cloudflare or a WAF may or may not help. These can often catch and block specific bot traffic, but not every attack payload is delivered naively. It would be part of a defense in depth. Having the underlying vulnerability fixed is critically important. For those on AWS, WAF & Shield is also very useful but at the end of the day these let legitimate traffic through, such as legitimately uploading a file that only in its contents is malformed.

ceejayoz 18 hours ago | |

Where does it say the site used Cloudflare?

shevy-java 16 hours ago |

DHH needs to focus on Rails again rather than Omarchy.

stephenhuey 14 hours ago | |

He’s still very supportive of Rails. Come join us at RailsWorld in Austin later this month and see for yourself!

dleink 5 hours ago | | |

I don't know. Austin isn't the city I fell in love with in the 90s and early 2000s. Chiefly because it's no longer full of native Texans.

tyre 16 hours ago | |

What does DHH have to do with this? Omarchy itself isn’t known for being secure; here is a root escalation from five days ago https://news.ycombinator.com/item?id=49499854

The rails developers are incredibly smart and capable. They patched the exploit. The problem is that it’s too easy to reverse engineer based on the patch. They can’t do anything about that.

dangond 14 hours ago | | |

> What does DHH have to do with this?

DHH created Rails.

kazinator 12 hours ago |

> That is about as bad as it gets and meant that any delay in patching was an existential risk of imminent compromise.

Overdramatized.

It means compromise if you delay patching and don't take the unpatched deployment offline.

Oh right, this is government sites; every second of down time is lost revenue.

bin/rails runner ' require "vips" puts "ruby-vips #{Vips::VERSION} libvips #{Vips.version(0)}.#{Vips.version(1)}.#{Vips.version(2)}" begin Vips::Operation.new("matload") puts "matload PRESENT - this build can reach libmatio" rescue Vips::Error puts "matload ABSENT - this build cannot reach libmatio" end '