CVE-2026-22808Network attack vector

Authentication-token theft via unvalidated MDM callback URL

Published Jan 21, 2026 · Updated Jan 21, 2026

Cross-site scripting in Fleet’s Windows MDM authentication flow allows remote attackers to steal an authenticated user’s Fleet token. The mdmMicrosoftAuthEndpoint passes the unvalidated appru callback parameter into STS response HTML, allowing injected JavaScript to read localStorage. Windows MDM must be enabled and the targeted user must open a malicious link; a stolen administrator token grants Fleet API access and privileged device actions.

CVSS severity5.5
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Fleet’s Windows MDM authentication flow allows remote attackers to steal an authenticated user’s Fleet token. The mdmMicrosoftAuthEndpoint passes the unvalidated appru callback parameter into STS response HTML, allowing injected JavaScript to read localStorage. Windows MDM must be enabled and the targeted user must open a malicious link; a stolen administrator token grants Fleet API access and privileged device actions.

The record

CVE
CVE-2026-22808
Published
Jan 21, 2026
Updated
Jan 21, 2026
Vendor
Fleet Device Management
Product
Fleet
Classifications
CWE-79, T1539
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.53.3
  2. Affected versionversion=>= 4.76.0, < 4.76.2
  3. Affected versionversion=>= 4.77.0, < 4.77.1
  4. Affected versionversion=>= 4.78.0, < 4.78.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Fleet Device Management · Fleetversion=< 4.53.3; version=>= 4.76.0, < 4.76.2; version=>= 4.77.0, < 4.77.1; version=>= 4.78.0, < 4.78.2

Published CVSS scores

5.5GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H
5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1539Steal Web Session Cookie

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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