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Vulnerability record · CVE-2026-26134 · published 10 March 2026

CVE-2026-26134: Microsoft 365 copilot integer overflow vulnerability

Microsoft · 365 Copilot

Integer overflow or wraparound in Microsoft Office allows an authorized attacker to elevate privileges locally.

7.8 CVSS 3.1 High EPSS 0.33% · top 76.0% CWE-190 · Integer overflowCWE-416 · Use after free
7.8CVSS 3.1 base score
0.33%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
1References
17 Jun 2026Last modified by NVD

Description

Integer overflow or wraparound in Microsoft Office allows an authorized attacker to elevate privileges locally.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26134 Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.9CVE-2026-50517Microsoft 365 copilot deserialization of untrusted data vulnerabilityDeserialization of untrusted data in M365 Copilot allows an authorized attacker to execute code over a network.EPSS 1.7%9.8CVE-2026-58617Microsoft 365 copilot improper access control vulnerabilityImproper access control in Microsoft 365 Copilot for iOS allows an unauthorized attacker to elevate privileges over a network.EPSS 0.79%9.8CVE-2025-60724Microsoft 365 copilot heap-based buffer overflow vulnerabilityHeap-based buffer overflow in Microsoft Graphics Component allows an unauthorized attacker to execute code over a network.EPSS 5.9%9.8CVE-2025-53766Microsoft 365 copilot heap-based buffer overflow vulnerabilityHeap-based buffer overflow in Windows GDI+ allows an unauthorized attacker to execute code over a network.EPSS 8.0%9.6CVE-2026-48561Microsoft 365 copilot command injection vulnerabilityImproper neutralization of special elements used in a command ('command injection') in Copilot Chat (Microsoft Edge) allows an unauthorized attacker …EPSS 0.86%9.6CVE-2021-43905Microsoft 365 copilot vulnerabilityMicrosoft Office app Remote Code Execution VulnerabilityEPSS 2.8%9.3CVE-2026-41106Microsoft 365 copilot open redirect vulnerabilityUrl redirection to untrusted site ('open redirect') in M365 Copilot allows an unauthorized attacker to elevate privileges over a network.EPSS 0.72%9.3CVE-2026-41090Microsoft 365 copilot command injection vulnerabilityImproper neutralization of special elements used in a command ('command injection') in Microsoft Copilot allows an unauthorized attacker to perform t…EPSS 0.76%

Source: NIST National Vulnerability Database (record CVE-2026-26134), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.