Description
EDK2 contains a vulnerability in BIOS where a user may cause “Out-of-bounds Write”, Classic Buffer Overflow, and “Incorrect Calculation of Buffer Size” by remote access. Successful exploitation of this vulnerability can lead to arbitrary code execution. It could also impact Confidentiality, Integrity, and Availability.
References6
- github.com/tianocore/edk2/security/advisories/GHSA-99cj-7hg9-mp…
- www.openwall.com/lists/oss-security/2026/10/28/4
- arstechnica.com/security/2026/10/code-execution-flaw-in-uefi-fi…
- github.com/microsoft/mu_basecore/pull/1989
- github.com/microsoft/mu_basecore/pull/1990
- news.ycombinator.com/item?id=50265393
Metrics
- CVSS 4.0
-
9.5
CRITICAL
Score source: CNA
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 1% percentile: 51 · as of 8 November 2026
- CWE
- CWE-120CWE-131CWE-787
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.