The flaw is CVE-2026-97631, rated 9.5 out of 10. It's a memory-corruption bug in an ICMP component of TianoCore EDK II, the open-source firmware codebase that most UEFI vendors (AMI, Insyde, Phoenix) and cloud providers build on. Microsoft's hardened fork, Project Mu, included the same code. Because it runs during boot, an attacker could run code before Secure Boot and the TPM start their checks. Payloads don't persist on their own, but they could install something that runs on every boot.
The disclosure was messy. Alex Matrosov (Anthropic) and Dan Holmes (Google) had planned a coordinated release for January. AMI published a pull request with the bug and its fix first, and TianoCore then issued an advisory. Ars Technica's Dan Goodin reports that the fix is public, which makes it easier for skilled attackers to work out how to trigger the bug.
Exposure is narrower than the headline suggests. One report says the flaw is reached through PXE network boot, which ships enabled by default, so machines that boot only from local disks are less exposed. Intel says its reference code leaves out the vulnerable feature, but OEMs may have included it, so it recommends checking with your system vendor. Arm says its products aren't directly affected.
What to do: check your server and motherboard vendors' advisories for firmware updates, and turn off PXE or network boot on machines that don't need it. Patching across many vendors will be slow, so treat this as a priority for the next firmware cycle.
🕒 As of October 2026
