CVE-2026-21245
Published: 10 February 2026
Summary
CVE-2026-21245 is a high-severity Heap-based Buffer Overflow (CWE-122) vulnerability in Microsoft Windows 11 24H2. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 11.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-16 (Memory Protection) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly mitigates the heap-based buffer overflow by requiring timely identification, reporting, and patching of the specific kernel vulnerability.
Implements memory protection mechanisms such as address space layout randomization and data execution prevention to block exploitation of the heap buffer overflow.
Enforces least privilege to limit the scope and impact of privilege escalation even if the kernel vulnerability is exploited by a low-privileged local attacker.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Heap buffer overflow in Windows Kernel directly enables local privilege escalation by low-privileged attacker (T1068).
NVD Description
Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.
Deeper analysisAI
CVE-2026-21245 is a heap-based buffer overflow vulnerability in the Windows Kernel that allows an authorized attacker to elevate privileges locally. Published on 2026-02-10T18:16:25.843, it is linked to CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write) and carries a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H), indicating high impact on confidentiality, integrity, and availability with low attack complexity.
A local attacker with low privileges (PR:L) can exploit this vulnerability due to its low requirements for access (AV:L) and no need for user interaction (UI:N). Successful exploitation enables privilege escalation on the affected Windows system, potentially granting the attacker higher-level access to resources and compromising the integrity of the kernel.
Mitigation details are available in the official advisory from the Microsoft Security Response Center at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21245.
Details
- CWE(s)