CVE-2026-26134
Published: 10 March 2026
Summary
CVE-2026-26134 is a high-severity Integer Overflow or Wraparound (CWE-190) vulnerability in Microsoft 365 Copilot. 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 15.1th 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-2 (Flaw Remediation) and AC-6 (Least Privilege).
Deeper analysis
CVE-2026-26134 is an integer overflow or wraparound vulnerability (CWE-190) in Microsoft Office, also associated with CWE-416. Published on 2026-03-10T18:18:42.803, it 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). The flaw enables an authorized attacker to elevate privileges locally within affected Microsoft Office installations.
A local attacker with low privileges (PR:L) can exploit this vulnerability with low attack complexity and no user interaction required. Successful exploitation grants high-impact access to confidentiality, integrity, and availability, primarily through local privilege escalation on the targeted system.
Microsoft's Security Response Center provides an update guide for mitigation at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26134.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-10699
Vulnerability details
Integer overflow or wraparound in Microsoft Office allows an authorized attacker to elevate privileges locally.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Local integer overflow/use-after-free in Microsoft Office directly enables T1068 Exploitation for Privilege Escalation (AV:L, PR:L, no UI, high CIA impact).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mandates timely remediation of known flaws, such as applying Microsoft patches for the integer overflow vulnerability in Office to prevent local privilege escalation.
Provides memory protections like ASLR and DEP that mitigate exploitation of integer overflow and associated memory corruption issues in Microsoft Office.
Enforces least privilege for user accounts and processes, limiting the scope and impact of privilege escalation from low-privilege local attackers exploiting the vulnerability.