Never have I ever piped curl to bash.
this post was submitted on 23 Feb 2026
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I never thought about opening it in a browser. I always used curl to download such a script and view it where it was supposed to be run.
Oh, people will keep using it no matter how much you warn them.
Proxmox-helper-scripts is a perfect example. They'll agree with you until that site comes up, and then its "it'll never, ever get hacked and subverted, nope, can't happen, impossible".
Wankers.
I was looking at that very thing last night.
But then I realized, "why can't immich just create usable packages like we had before?" and moped back out.
But, for a moment, I was sure a little inspection and testing would make the Internet equivalent of NYC MTA coin-sucking magically safe. It looked so eeeeasy.
This helped a lot. I had no clue I could post the curl string in the URL bar of a browser to view the script. Thanks for the education!
You had no idea you could paste a url into a browser's location bar ?
You didn't knew that the tool to handle URLs written in C (very creatively named C-Url) was handling URLs? It's also written in C if you didn't knew.
Yes this has risks. At the same time anytime you run any piece of software you are facing the same risks, especially if that software is updated from the internet. Take a look at the NIST docs in software supply chain risks.
But those are two very different things, I can very easily give you a one liner using curl|bash that will compromise your system, to get the same level of compromise through a proper authenticated channel such as apt/pacman/etc you would need to compromise either their private keys and attack before they notice and change them or stick malicious code in an official package, either of those is orders of magnitude more difficult than writing a simple bash script.
This is a bit like saying crossing the street blindfolded while juggling chainsaws and crossing the street on a pedestrian crossing while the light is red for cars both carry risk. Sure. One's a terrible idea though.
Not completely correct. A lot of updaters work with signatures to verify that what was downloaded is signed by the correct key.
With bash curl there is no such check in place.
So strictly speeking it is not the same.
Signatures do not help if your distribution infra gets compromised. See Solarwinds and the more recent node.js incidents.
Please tell me you are not seriously equating a highly sophisticated attack line the Solarwind compromise with piping curl to bash?
This is incorrect. If the update you download is compromised then the signature is invalid and the update fails.
To achieve a compromised update you either need to compromise the update infrastructure AND the key or the infratstructure AND exploit the local updater to accept the invalid or forged signature.
If I can control your infra I can alter what is a valid signature. It has happened. It will happen again. Digital signatures are not sufficient by themselves to prevent supply chain risks. Depending on your threat model, you need to assume advanced adversaries will seek to gain a foothold in your environment by attacking your software supplier. in these types of attacks threat actors can and will take control over the distribution mechanisms deploying trojaned backdoors as part of legitimately signed updates. It is a complex problem and I highly encourage you to read the NIST guidance to understand just how deep the rabbit hole goes.
Cybersecurity Supply Chain Risk Management Practices for Systems and Organizations
No you cannot, the pub key either needs to be present on the updater or uses infrastructure that is not owned by you. Usually how most software suppliers are doing it the public key is supplied within the updater.
Not sure how else to explain this. Look at the CISA bulletin on Shai-Hulud the attacker published valid and signed binaries that were installed by hundreds of users.
"CISA is releasing this Alert to provide guidance in response to a widespread software supply chain compromise involving the world’s largest JavaScript registry, npmjs.com. A self-replicating worm—publicly known as “Shai-Hulud”—has compromised over 500 packages.[i]
After gaining initial access, the malicious cyber actor deployed malware that scanned the environment for sensitive credentials. The cyber actor then targeted GitHub Personal Access Tokens (PATs) and application programming interface (API) keys for cloud services, including Amazon Web Services (AWS), Google Cloud Platform (GCP), and Microsoft Azure.[ii]
The malware then:
- Exfiltrated the harvested credentials to an endpoint controlled by the actor.
- Uploaded the credentials to a public repository named
Shai-Huludvia theGitHub/user/reposAPI. - Leveraged an automated process to rapidly spread by authenticating to the npm registry as the compromised developer, injecting code into other packages, and publishing compromised versions to the registry.[iii]"
After gaining initial access, the malicious cyber actor deployed malware that scanned the environment for sensitive credentials.
So as I said, the keys got compromised. Thats what i said in the second post.
What you said is the key infra needs to get compromise. I do not need to own the PKI that issued the certs, I just need the private key of the signer. And again, this is something that happens. A lot. A software publisher gets owned, then their account is used to distribute malware.
To achieve a compromised update you either need to compromise the update infrastructure AND the key or the infratstructure AND exploit the local updater to accept the invalid or forged signature.
As i said, to compromise a signature checked update over the internet you need to compromise both, the distributing infrastructure AND the key. With just either one its not possible. (Ignoring flaws in the code ofc)
Apt is great
a more cautious user might first paste the url into the address bar of their web browser to see what the script looks like before running it.
Wow, I never thought anyone would be that dumb.
Why wouldn't they just wget it, read it, and then execute it?
Oh the example in the article is the nice version if this attack.
Checking the script as downloaded by wget or curl and then piping curl to bash is still a terrible idea, as you have no guarantee you'll get the same script in both cases:
Anytime I see a project that had this in their install instructions, I don't use that project.
It shows how dumb the devs are
Yes, this is the correct approach from a security perspective.
@K3can@lemmy.radio love the early 2000s stylesheet/color theme of your blog 🙂
Thanks! I like to keep things simple. The colors are based on Counter Strike 1.6. 😁
And if you're into the classic styling, my homepage is a direct homage to my old 2000s sites.
You mean blindly running code is bad? /s
Curl bash is no different than running an sh script you dont know manually…
No, it is different, as it adds an entire layer of indirection and unknown to the mix, increasing the risk in the process.
True, but this is specifically about scripts you think you know, and how curl bash might trick you into running a different script entirely.
you’d have to be mad to willingly pipe a script to bash without checking it. holy shit
Is it different from running a bash script you downloaded without checking it? E.g. the installer that you get with GOG games?
Genuine question, I'm no expert.
It is, see https://github.com/m4tx/curl-bash-attack
That's an interesting proof of concept, but I don't think it shows it's different. That's a server side attack, whoever has control of the server could just have the script download a malicious binary instead and you wouldn't be able to tell from the script.
It's really only about trusting the source. Your operating system surely has thousands of scripts that you've never read and never checked. And wouldn't have time to. And people don't complain about that.
But it's really bad practice to run random things from random sites. So the practice of downloading a script and running it is frowned upon. Mostly as a way of maintaining good security hygiene.
I have no problems with running scripts from the internet, AFTER you check them. Do NOT blindly run a script you found on the internet. As others have said download them, then check them, then and only then run them if they're safe. NEVER pipe to bash, ever.
Ok but not everyone has that skill. And anyway, how is this different to running a binary where you can't check the code?
it's exactly the same. Don't run binaries you don't trust fully. But i get what you mean. miley_cyrus_nude.jpg.exe is probably gonna end badly.
Yeah I get that, but I would install docker, cloudflared, etc by piping a convenience script to bash without hesitation. I've already decided to install their binary, I don't see why the install script is any higher risk.
I know it's a controversial thing for everyone to make their own call on, I just don't think the risk for a bash script is any higher than a binary.
I won't lie, I use curl | bash as well, but I do dislike it for two reasons:
Firstly, it is much, much easier to compromise the website hosting than the binary itself, usually. Distributed binaries are usually signed by multiple keys from multiple servers, resulting in them being highly resistant to tampering. Reproducible builds (two users compiling a program get the same output) make it trivial to detect tampering as well.
On the other hand, websites hosting infrastructure is generally nowhere near as secure. It's typically one or two VPS's, and there is no signature or verification that the content is "official". So even if I'm not tampering with the binary, I can still tamper with the bash script to add extra goodies to it.
On the other hand (but not really relevant to what OP is talking about), just because I trust someone to give me a binary in a mature programming language they have experience writing in, doesn't mean I trust them to give me a script in a language known for footguns. A steam bug in their bash script once deleted a user's home directory. There have also been issues with AUR packages, which are basically bash scripts, breaking people's systems as well. When it comes to user/community created scripts, I mostly trust them to not be malicious, and I am more fearful of a bug or mistake screwing things up. But at the same time, I have little confidence in my ability to spot these bugs.
Generally, I only make an exception for running bash installers if the program being installed is a "platform" that I can use to install more software. K3s (Kubernetes distro), or the Nix package manager are examples. If I can install something via Nix or Docker then it's going to be installed via there and not installed via curl | bash. Not every developer under the sun should be given the privilege of running a bash script on my system.
As a sidenote, docker doesn't recommend their install script anymore. All the instructions have been removed from the website, and they recommend adding their own repo's instead. Personally, I prefer to get it from the distro's repositories, as usually that's the simplest and fastest way to install docker nowadays.
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Most developers I've looked at would happily just paste the curl|bash thing into the terminal.
I often would skim the script in the browser, but a. This post shows that's not fool proof and b. a sufficiently sophisticated malicious script would fool a casual read
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And it's wild how much even that has been absolutely normalized by all these shitty lazy developers and platforms. Vibe coding it just going to make it worse. All these programs that look nice on the surface and are just slop on the inside. It's going to be a mess.
And you better inspect and execute a downloaded copy, because a malicious actor can serve a different file for curl/wget than to your browser
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In addition to the other examples it's also in the default installation mode for node.js - they use this to install nvm
Ya cant even blame someone non-technical falling for this if they haven't been explicitly informed - it's getting reinforced as completely normal by too many "reputable" projects.
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The post is specifically about how you can serve a totally different script than the one you inspect. If you use curl to fetch the script via terminal, the webserver can send a different script to a browser based on the UserAgent.
And whether or not you think someone would be mad to do it, it's still a widespread practice. The article mentions that piping curl straight to bash is already standard procedure for Proxmox helper scripts. But don't take anyone's word for it, check it out:
https://community-scripts.github.io/ProxmoxVE/
It's also the recommended method for PiHole:
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