CVE-2026-24899: Github.com/fleetdm/fleet/v4 Authentication Bypass Vulnerability

HIGH
Advisory Identifier: GHSA-ffg9-j72f-j6xm
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CVSS 7.5
CWE-290
Published
Advisory Summary

CVE-2026-24899 is a HIGH (CVSS 7.5) authentication bypass vulnerability (CWE-290: Authentication Bypass by Spoofing) affecting Github.com/fleetdm/fleet/v4 libraries in the Go ecosystem. The issue involves fleet windows mdm azure ad jwt authentication bypass. Remediation is available by upgrading affected packages to version 4.82.0.

CVE-2026-24899 at a Glance

CVE Identifier CVE-2026-24899
GHSA Identifier GHSA-ffg9-j72f-j6xm
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-290: Authentication Bypass by Spoofing
Affected Product Github.com/fleetdm/fleet/v4
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-24899

To remediate this vulnerability, upgrade all affected Github.com/fleetdm/fleet/v4 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/fleetdm/fleet/v4 fixed: 4.82.0 
Upgrade github.com/fleetdm/fleet/v4 to 4.82.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/fleetdm/fleet/v4

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-24899, inspect your project dependencies for Github.com/fleetdm/fleet/v4:

inspect dependencies for github.com/fleetdm/fleet/v4

Analyze the terminal output to locate any version of Github.com/fleetdm/fleet/v4 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.82.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-290: Authentication Bypass by Spoofing, where this attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks. In Github.com/fleetdm/fleet/v4, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary A vulnerability in Fleet's Windows MDM enrollment flow allows authentication tokens from any Azure AD tenant to be accepted. Because Fleet validates JWT signatures using Microsoft's multi-tenant JWKS endpoint but does not enforce the `aud` (audience) or `iss` (issuer) claims, any Microsoft-signed Azure AD access token containing the expected scopes can be used to authenticate to Fleet's MDM endpoints. ### Impact If Windows MDM is enabled, an attacker with access to any Azure AD tenant can obtain a valid Microsoft-signed token and use it to enroll unauthorized devices and interact with Fleet's MDM management APIs. During device management, Fleet may expose sensitive enrollment secrets embedded in MDM command payloads, enabling further unauthorized access. ### Workarounds If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM. ### For more information If you have any questions or comments about this advisory: Email us at [security@fleetdm.com](mailto:security@fleetdm.com) Join #fleet in [osquery Slack](https://join.slack.com/t/osquery/shared_invite/zt-h29zm0gk-s2DBtGUTW4CFel0f0IjTEw) ### Credits We thank @zaddy6 for responsibly reporting this issue.

CVE-2026-24899 Affected Github.com/fleetdm/fleet/v4 Versions

1 component(s)
Fixed Versions:
4.82.0
Product / Package Ecosystem Affected Versions Fixed Version
github.com/fleetdm/fleet/v4
golang/github.com/fleetdm/fleet/v4
Go
< 4.82.0
4.82.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/fleetdm/fleet/security/advisories/GHSA-ffg9-j72f-j6xm
NVD — CVE-2026-24899 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-24899
Github.com/fleetdm/fleet/v4 Source Repository REPOSITORY
https://github.com/fleetdm/fleet
Github.com/fleetdm/fleet/v4 Release RELEASE
https://github.com/fleetdm/fleet/releases/tag/fleet-v4.82.0

Frequently Asked Questions

What is CVE-2026-24899?
CVE-2026-24899 is a security vulnerability in Github.com/fleetdm/fleet/v4 involving Fleet Windows MDM Azure AD JWT Authentication Bypass under CWE-290: Authentication Bypass by Spoofing.
Which Github.com/fleetdm/fleet/v4 versions are affected?
Affected versions include releases prior to 4.82.0 across affected packages: github.com/fleetdm/fleet/v4.
What version fixes CVE-2026-24899?
Upgrading to 4.82.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/fleetdm/fleet/v4 affected?
Yes, github.com/fleetdm/fleet/v4 is affected in releases prior to 4.82.0. Upgrade your dependency to 4.82.0 or later.
What is the CVSS score of CVE-2026-24899?
CVE-2026-24899 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-24899?
CVE-2026-24899 is classified under CWE-290: Authentication Bypass by Spoofing (This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.).
How can I check Go dependencies for CVE-2026-24899?
Run the dependency tree command: 'inspect dependencies for github.com/fleetdm/fleet/v4'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-ffg9-j72f-j6xm",
  "modified" : "2026-06-08T23:26:12Z",
  "published" : "2026-05-14T13:13:56Z",
  "aliases" : [ "CVE-2026-24899" ],
  "summary" : "Fleet Windows MDM Azure AD JWT Authentication Bypass",
  "details" : "### Summary\n\nA vulnerability in Fleet's Windows MDM enrollment flow allows authentication tokens from any Azure AD tenant to be accepted. Because Fleet validates JWT signatures using Microsoft's multi-tenant JWKS endpoint but does not enforce the `aud` (audience) or `iss` (issuer) claims, any Microsoft-signed Azure AD access token containing the expected scopes can be used to authenticate to Fleet's MDM endpoints.\n\n### Impact\n\nIf Windows MDM is enabled, an attacker with access to any Azure AD tenant can obtain a valid Microsoft-signed token and use it to enroll unauthorized devices and interact with Fleet's MDM management APIs. During device management, Fleet may expose sensitive enrollment secrets embedded in MDM command payloads, enabling further unauthorized access.\n\n### Workarounds\n\nIf an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM.\n\n### For more information\n\nIf you have any questions or comments about this advisory:\nEmail us at [security@fleetdm.com](mailto:security@fleetdm.com)\nJoin #fleet in [osquery Slack](https://join.slack.com/t/osquery/shared_invite/zt-h29zm0gk-s2DBtGUTW4CFel0f0IjTEw)\n\n### Credits\n\nWe thank @zaddy6 for responsibly reporting this issue.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/fleetdm/fleet/v4"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.82.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/fleetdm/fleet/security/advisories/GHSA-ffg9-j72f-j6xm"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-24899"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/fleetdm/fleet"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/fleetdm/fleet/releases/tag/fleet-v4.82.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-290" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-14T13:13:56Z",
    "nvd_published_at" : "2026-05-14T20:17:01Z"
  }
}