Linux and Secure Boot certificate expiration (2025) | Hacker News Reader

Linux and Secure Boot certificate expiration (2025)

lwn.net

130 pointsweaksauce66 comments

They left out the steps to update it. I made a rough attempt at a document for this. [1] Please let me know if I missed a validation step. I have done this on six machines but they were all Linux. Not tested on BSD.

Archive [2] in the event I was too aggressive in blocking bots.

[Edit] I should also include this [3] thread for completeness sake. Some people people were playing with a shim work around but it looks like a lot of unnecessary complexity and fragility to me.

[1] - https://nochan.net/b/Internet-Crap/20260621-Update-Secure-Bo...

[2] - https://archive.is/ml3jv

[3] - https://www.reddit.com/r/archlinux/comments/1pvw6td/grub_shi...

Found this on one machine. Key expires in 5 days. System runs Linux only and has never booted Windows, ever. Secure boot may be off.

    SHA1 Fingerprint: 46:de:f6:3b:5c:e6:1c:f8:ba:0d:e2:e6:63:9c:10:19:d0:ed:14:f3
    Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            61:08:d3:c4:00:00:00:00:00:04
        Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=US, ST=Washington, L=Redmond, O=Microsoft Corporation, CN=Microsoft Corporation Third Party Marketplace Root
        Validity
            Not Before: Jun 27 21:22:45 2011 GMT
            Not After : Jun 27 21:32:45 2026 GMT
        Subject: C=US, ST=Washington, L=Redmond, O=Microsoft Corporation, CN=Microsoft Corporation UEFI CA 2011

I had to vouch your comment, not sure what happened there. Something in your technical output must have triggered HN. One can use mokutil to see if Secure Boot is enabled after installing it. I assume the OEM installation or update of the BIOS must have included that cert but I am just guessing.

    mokutil --sb-state

Thanks.

Just checked. Secure Boot is not enabled on any of my machines, which are Linux-only. Whew!

(I wonder if any of the ASUS subnotebooks I bought off eBay for minor embedded stuff have this problem. Have to power them up.)

My ASUS laptop had it enabled. I had to disable it as there just wasn't enough non volital memory to hold all the updates even after remove several EFI entries and resetting the BIOS. All my mini-PC's updated fine however. My Linux Protectli routers already had it disabled thankfully. They use Coreboot, unsure if that was a factor.

FYI your server returns Brotli encoded content, even if the request has only Accept-Encoding: gzip, deflate, zstd - making it unreadable in for me (Firefox on Fedora).

I actually did that on purpose since all browsers support brotli I risked the possibility someone might have disabled it with an add-on. I wanted to see how many bots that would break. It may not be the most logical process but I just use CanIUse [1] to see what supports Brotli. I ignore the Opera Mini block as they seem to support almost nothing.

[1] - https://caniuse.com/brotli

Ah, fair enough. Well Firefox should support Brotli by default, so it's probably something going on on my machine.

Nothing wrong with that. I think people should be able to disable anything they want. I doubt any commercial sites will do what I am doing. I use that little blog to test all manor of unorthodox things. That's why I listed the archive mirror, just in case.

I've seen commercial sites hard-code gzip content in all their responses regardless of the Accept headings. Probably just as fair to use Brotli these days.

Similarly, I've been using zopfli (gzip/unzip compatible) for png compression after quantization for db storage from 2-color (B/W) scans as it's directly compatible to the browser but winds up about 1/6 the original sized tiff. Not the best compression, had a discussion for a better compression, but required a wasm renderer to decompress as it isn't in the browser box.

More recent archive [1]

[1] - https://archive.is/dPFuq

> The KEK updates are going out at ~98% success, and db update is ~99% success

glad to see the opt in fwupd analytics being so useful for something like this

Not envious of the running around contacting vendors they must of been doing on such short order.

Last time I installed Arch, I put Secure Boot in setup mode and enrolled by own keys. The idea of using someone else's keys seems absurd.

I've honestly always kept secure boot off on my machines (which also use Arch). I don't really feel like the level of threat from someone (or me, by accident) booting an image I don't want them to on my hardware is particularly worth the hassle it brings; nobody else should ever be using my machines in the first place, and if they are, I'm going to have larger issues than what OS they decide to try to boot.

I'm inclined to agree when it comes to desktops or servers. However I feel like a laptop needs better security, including secure boot and full disk encryption, since you could lose it and cannot be sure what it went through even if you get it back somehow.

I do use FDE on my laptop, but not secure boot. I guess I'm not particularly concerned about whether someone will load a kernel onto my boot partition and then return the laptop to me. I could always just clear out my boot partition and then set it up manually again from an Arch USB, and that would still be far less hassle than turning in secure boot.

> nobody else should ever be using my machines in the first place, and if they are, I'm going to have larger issues than what OS they decide to try to boot.

The threat model secure boot was actually designed to protect against is not someone else booting a different OS in your hardware; the real threat model it protects against is malware loading before the OS can start the antivirus. With UEFI, malware could in theory run even when you boot from your OS install media, making it much harder to detect and remove. That's the reason installing your own secure boot key requires a one-time confirmation through a physical input device (which malware can't fake).

Unfortunately, protecting against that threat model (persistent malware loading before the OS) created another threat model, which IMO is a bigger worry: that you could one day be forbidden from running your own OS in your own devices. AFAIK, there have already been a few devices where secure boot cannot be disabled, your own secure boot keys cannot be enrolled, and the "third party" (aka "non-Microsoft") key is not available.

Do note that being able to completely remove MS keys is highly dependent on your mainboard. Not in the sense of if they allow you to do it (I think most if not all DIY boards allow you to), but if you will be able to boot afterwards.

I (soft?)bricked a mainboard and it doesn't want to boot anymore after I removed the MS keys. The worst part is, that it has a dualBIOS and no active switch to change between them, only their own "I'll change when I see issues"... well you can guess how well that worked out (and I am not able to get it to clear CMOS for some reason).

I saw 2-3 flavors of this news. None of them include a basic “how do I check if I need to do anything” guide that a linux newbie can do.

On my Fedora machine I was able to run

    mokutil --db --short

To check my secure boot keys. As long as there's 2023 Microsoft keys you should be fine. Otherwise, my understanding is that you just need to update your firmware, but please somebody correct me if I'm wrong.

https://wiki.debian.org/SecureBoot/CAChanges#What_should_I_d...

> triggering a "de-fragmentation" of the available efivar space so that there's enough contiguous space to deploy the update.

I didn't even realize this could be a problem despite the next paragraph implying it's very well known.

Discussed at the time (of the article):

Linux and Secure Boot certificate expiration - https://news.ycombinator.com/item?id=44601045 - July 2025 (265 comments)

I'm surprised more people aren't freaking out about this. It seems likely a whole lot of Linux machines are going to fail to reboot in the next few months. The problem affects VMs too. I was grateful Proxmox put a little warning in its hypervisor GUI with a button to press to fix the BIOS of its VMs.

Secure Boot has been deeply broken for years, not providing meaningful security on most consumer machines.

Why has it been broken? I’m running secure boot on all my machines with my own certs. It works fine.

Whatever ms and hp / Lenovo do with their certs doesn’t affect me, since I only have my certs installed. Except on a single machine whose purpose is running windows, but it’s not on the critical path for my job.

numerous vulnerabilities in secure boot deployment over many years. e.g. https://arstechnica.com/security/2024/09/secure-boot-neuteri...

I don't have any numbers to prove it, but I'd say the reason Linux users aren't freaking out is because the vast majority of them would've have disabled Secure Boot. In fact, many guides and videos from popular Youtubers[1] explicitly state to disable Secure Boot.

As for VMs, whilst the problem indeed affects them too, the reality is that most hypervisors - even commercial ones - don't actually enable Secure Boot by default, you'd have to go really out of your way to enable it for a VM.

[1] https://www.youtube.com/watch?v=_Ua-d9OeUOg&t=253

My very recent story with libvirt and secureboot resulted in blanket disabling of secureboot as part of the preparation for creation of VMs.

The reason: the VM refuses to boot when provided with an ISO (via virtual CDROM) with a meaningless error (permission denied: go figure out what permission and why was it denied and by whom).

Secureboot is meaningless / useless for most people running VMs, be it on own or rented hardware. It takes some pain and extra work to get it to work sometimes, and a huge amount of work to get it to work always. I doubt anyone was dedicated enough to get it to work always. So, I believe you are right. This is extremely unlikely to be a problem for anyone running Linux VMs, and the more VMs they need to run, the less likely it is a problem.

Existing systems are going to continue to boot. The expiry date is enforced for signing new binaries, not for deciding whether an already signed binary is allowed to boot (barring buggy firmware).

https://mjg59.dreamwidth.org/72892.html (Secure boot certificate rollover is real but probably won't hurt you)

https://wiki.debian.org/SecureBoot/CAChanges#OMG.21.21.21_Wi...

> he expiry date is enforced for signing new binaries

Does this means that updating my system kernel would fail or even break boot?

No, distros uses a shim binary that is less likely to need updates. If that shim needs an update (only signed with the new key) then we get into a situation where old machines will fail to boot it.

Shim, the first stage bootloader on Linux, is designed to be updated infrequently. Distributions embed their own signing certificate in it and have that binary signed by Microsoft. The actual bootloader (typically either grub or systemd-boot) is then signed with the distribution certificate, as is the kernel. Distributions get to set their own policy around how long that certificate lasts for, it's entirely unrelated to the Microsoft certificate expiry.

Well, it seems like keeping secure boot disabled was gonna help me in the future haha

I know it is not recommended but the options to have my own keys seemed a bit of a hack than a solution.

Some laptops allow Custom Mode in UEFI setup menu. Then you can clear these keys and load your own. On Linux etc. you can that way enable secure boot without MS keys.

Not all devices support it, so choose wisely.

How do desktop Linux distros avoid attackers from rolling back the operating system to a vulnerable, but signed version?

This is not an issue specific to Linux, Windows installations can be downgraded as well. As for the mechanism, UEFI devices, alongside key updates, also get revocation list updates.

Strangely I feel like I've never seen one of these. It would be needed after every major kernel / user land exploit. It would also need rollback protection on the motherboard itself so you couldn't just remove the updated keys / revocations.

It needs to be said, this is what you get by "trusting" Microsoft.

There really is no need for secure boot in Linux. The only reason to have it is if you dual boot because M/S says so. If using Linux by itself, just disable secure boot and have done with it.

I don’t know why we ended up trusting microslop. Red Hat implemented it for the sake of convenience causing all these issue.

I disagree that there is no need for secure boot for Linux?

Secure boot prevents tampering of your kernel and/or bootloader, nothing about Linux prevents this from being possible.

You might argue that you don't care about this, but some people such as myself do!

> Secure boot prevents tampering of your kernel and/or bootloader, nothing about Linux prevents this from being possible.

By trusting another chain of trust and firmware binary blobs involved in booting your PC.

Secure boot exists only as one of the puzzle pieces for remote attestation for MS and trusted OEMs, nothing to do with your security.

>By trusting another chain of trust and firmware binary blobs involved in booting your PC.

So what? I'm still preventing a random person from tampering with my bootloader?

If you want yourself to be the root of trust, you CAN generate and use your own keys for secure boot.

The word from Red Hat is existing systems will continue to boot — presumably because they are time-stamped and counter-signed or because the dates are ignored entirely.

99% of secure boot discussions are drowned out by people who don't have a clue what they're talking about, yet are spittingly, furiously mad.

They've also had over a year to prepare for this so if Linux distros are only telling you now, that's on them.

> 99% of secure boot discussions are drowned out by people who don't have a clue what they're talking about, yet are spittingly, furiously mad.

Well yea - as someone who has 0 understanding of why we need it, and only ever get greatly frustrated by it, I am pretty mad that people feel entitled to call my distro managers "that's on them"

IIRC UEFI firmwares do not check the expiry date, they don't care that the certificate has expired at all. There's no risk of any existing .efi binaries suddenly not loading.

The issue seems to be that Microsoft will refuse to sign anything new with the expiring certificate (which is correct behaviour), so any UEFI firmware that hasn't got the new certificate will refuse newly signed bootloaders.

I don't see anything wrong with this scenario, it's on distros to properly make sure they're distributing secure boot certificate updates.

Edit: Apparently RHEL will even refuse to install a 2023 signed shim if the firmware lacks the certificate for it.

> Apparently RHEL will even refuse to install a 2023 signed shim if the firmware lacks the certificate for it.

Why is that? RHEL own blog post described that RHEL is distributing dual signed shim by both 2011 and 2023 certificates, so that it works either way, only 2011 present or only 2023.

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