CVE-2026-97631
Critical9.5EDK2: Pre-boot RCE in EDK II PXE drivertitle from the CVE record
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.
- CVSS
- 9.5v4.0
- EPSS (exploit probability)
- 0.4%37th pct
- CISA KEV
- Not listed
EPSS trendFIRST daily scores, last 90 days
Daily values
| Score date | EPSS | Percentile |
|---|---|---|
| 2026-10-27 | 0.4% | 37.4% |
| 2026-10-26 | 0.4% | 37.3% |
| 2026-10-25 | 0.4% | 37.3% |
| 2026-10-24 | 0.4% | 36.6% |
| 2026-10-23 | 0.4% | 36.5% |
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
Learn
Why it happened and what stops it
The weakness (CWE)
- CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')Input is copied into a fixed-size buffer without checking its length, overwriting whatever follows.
- CWE-131Incorrect calculation of buffer size
- CWE-787Out-of-bounds WriteData is written outside the memory it belongs to; the most common root cause of exploited memory bugs.
How attackers use it (ATT&CK)
Typical for this kind of weakness across CISA KEV exploits (CTID), not specific to this CVE.
How it's exploited
What the attacker gets
Controls that mitigate it (NIST SP 800-53)
- SI-3Malicious Code ProtectionSystem and Information Integrity · mitigates 8 of these techniques
- SI-4System MonitoringSystem and Information Integrity · mitigates 8 of these techniques
- CA-7Continuous MonitoringSecurity Assessment and Authorization · mitigates 7 of these techniques
- CM-6Configuration SettingsConfiguration Management · mitigates 7 of these techniques
- CM-7Least FunctionalityConfiguration Management · mitigates 7 of these techniques
- AC-4Information Flow EnforcementAccess Control · mitigates 6 of these techniques