Cross-Site Scripting in Fleet MDM Enables Admin Token Theft

Publication date: 2026-01-21

Last updated on: 2026-02-18

Assigner: GitHub, Inc.

Description

fleetdm/fleet is open source device management software. Prior to versions 4.78.2, 4.77.1, 4.76.2, 4.75.2, and 4.53.3, if Windows MDM is enabled, an unauthenticated attacker can exploit this XSS vulnerability to steal a Fleet administrator's authentication token (FLEET::auth_token) from localStorage. This could allow unauthorized access to Fleet, including administrative access, visibility into device data, and modification of configuration. Versions 4.78.2, 4.77.1, 4.76.2, 4.75.2, and 4.53.3 fix the issue. If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM.

CVSS Scores

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Meta Information

Published

2026-01-21

Last Modified

2026-02-18

Generated

2026-07-06

AI Q&A

2026-01-22

EPSS Evaluated

2026-07-05

NVD

CVE-2026-22808

Affected Vendors & Products

Vendor	Product	Version / Range
fleetdm	fleet	to 4.53.3 (exc)
fleetdm	fleet	From 4.75.0 (inc) to 4.75.2 (exc)
fleetdm	fleet	From 4.76.0 (inc) to 4.76.2 (exc)
fleetdm	fleet	From 4.78.0 (inc) to 4.78.2 (exc)
fleetdm	fleet	4.77.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-79	The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

Attack-Flow Graph

Executive Summary

This vulnerability is a cross-site scripting (XSS) issue in fleetdm/fleet device management software when Windows MDM is enabled. An unauthenticated attacker can exploit this XSS flaw to steal a Fleet administrator's authentication token (FLEET::auth_token) from localStorage, potentially gaining unauthorized administrative access to the Fleet system.

Impact Analysis

If exploited, this vulnerability can allow an attacker to gain unauthorized access to the Fleet system with administrative privileges. This includes the ability to view device data and modify configuration settings, which could compromise the security and management of devices under Fleet's control.

Mitigation Strategies

To mitigate this vulnerability immediately, upgrade Fleet to versions 4.78.2, 4.77.1, 4.76.2, 4.75.2, or 4.53.3 where the issue is fixed. If an immediate upgrade is not possible, temporarily disable Windows MDM.

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