CVE-2026-26144
Published: 10 March 2026
Summary
CVE-2026-26144 is a high-severity Cross-site Scripting (CWE-79) vulnerability in Microsoft 365 Apps. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 30.4th 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-10 (Information Input Validation) and SI-15 (Information Output Filtering).
Deeper analysis
CVE-2026-26144, published on 2026-03-10, is a cross-site scripting (XSS) vulnerability classified under CWE-79 in Microsoft Office Excel. The issue arises from improper neutralization of input during web page generation, enabling an unauthorized attacker to disclose information over a network. It has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N), indicating high severity due to network accessibility, low attack complexity, and no requirements for privileges or user interaction.
An unauthorized attacker can exploit this vulnerability remotely without authentication or user involvement. Exploitation allows the attacker to achieve high-impact information disclosure over the network, potentially exposing sensitive data contained in or accessible via the affected Excel component, while leaving integrity and availability unaffected.
The Microsoft Security Response Center advisory provides details on mitigation and patches at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26144.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-10701
Vulnerability details
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office Excel allows an unauthorized attacker to disclose information over a network.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote network-accessible XSS (CWE-79) in Excel's web page generation directly maps to exploitation of a (web) application (T1190) and arbitrary JavaScript execution (T1059.007); the stated high-impact information disclosure enables data collection from the local system/browser context (T1005).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly addresses improper neutralization of input during web page generation by filtering outputs to prevent XSS exploitation and information disclosure.
Validates untrusted inputs to Microsoft Office Excel to neutralize malicious content before web page generation.
Remediates the specific XSS flaw in Microsoft Office Excel through identification, reporting, and application of vendor patches.