Microsoft breaks some Linux dual-boots in a recent Windows update

Do you dual-boot Windows and Linux? Well, a recent Windows update seems to have been a bit messy and may have broken the ability to boot into Linux. Causing an alarming message to display of "Something has gone seriously wrong".

The update in question is in relation to CVE-2022-2601, and as the numbers there suggests, it's an issue from way back in 2022 that Microsoft decided just last week to go and patch up themselves. From the CVE:

A buffer overflow was found in grub_font_construct_glyph(). A malicious crafted pf2 font can lead to an overflow when calculating the max_glyph_size value, allocating a smaller than needed buffer for the glyph, this further leads to a buffer overflow and a heap based out-of-bounds write. An attacker may use this vulnerability to circumvent the secure boot mechanism.

It wasn't supposed to affect you if you do have Linux installed, as per Microsoft's own info they said:

To address this security issue, Windows will apply a Secure Boot Advanced Targeting (SBAT) update to block vulnerable Linux boot loaders that could have an impact on Windows security. The SBAT value is not applied to dual-boot systems that boot both Windows and Linux and should not affect these systems. You might find that older Linux distribution ISOs will not boot. If this occurs, work with your Linux vendor to get an update.

However, that seems to have still caused problems for those that do dual-boot. Oops. There's been quite a few reports of people unable to boot into their Linux distributions as a result of this update. A potential solution can be found in an Ubuntu Discourse post from 2023 for a previous issue.

Microsoft haven't yet said anything about it that I can find, and their update page notes "Microsoft is not currently aware of any issues with this update", so clearly that needs an update.