Vulnerability-Lookup

CVE-2026-23518 (GCVE-0-2026-23518)

Vulnerability from cvelistv5 – Published: 2026-01-21 21:50 – Updated: 2026-01-22 16:49

Title

Fleet has a JWT signature bypass vulnerability in Azure AD MDM enrollment

Summary

Fleet is open source device management software. In versions prior to 4.78.3, 4.77.1, 4.76.2, 4.75.2, and 4.53.3, a vulnerability in Fleet's Windows MDM enrollment flow could allow an attacker to submit forged authentication tokens that are not properly validated. Because JWT signatures were not verified, Fleet could accept attacker-controlled identity claims, enabling enrollment of unauthorized devices under arbitrary Azure AD user identities. Versions 4.78.3, 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.

Severity ?

9.3 (Critical)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CWE

CWE-347 - Improper Verification of Cryptographic Signature

Assigner

GitHub_M

References

URL

Tags

	https://github.com/fleetdm/fleet/security/advisor…	x_refsource_CONFIRM
	https://github.com/fleetdm/fleet/commit/e225ef579…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	fleetdm	fleet	Affected: >= 4.78.0, < 4.78.3 Affected: >= 4.77.0, < 4.77.1 Affected: >= 4.76.0, < 4.76.2 Affected: >= 4.75.0, < 4.75.2 Affected: < 4.53.3

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-23518

Vulnerability from fkie_nvd - Published: 2026-01-21 22:15 - Updated: 2026-01-21 22:15

Severity ?

9.3 (Critical) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/fleetdm/fleet/commit/e225ef57912c8f4ac8977e24b5ebe1d9fd875257
	security-advisories@github.com	https://github.com/fleetdm/fleet/security/advisories/GHSA-63m5-974w-448v

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Fleet is open source device management software. In versions prior to 4.78.3, 4.77.1, 4.76.2, 4.75.2, and 4.53.3, a vulnerability in Fleet\u0027s Windows MDM enrollment flow could allow an attacker to submit forged authentication tokens that are not properly validated. Because JWT signatures were not verified, Fleet could accept attacker-controlled identity claims, enabling enrollment of unauthorized devices under arbitrary Azure AD user identities. Versions 4.78.3, 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."
    }
  ],
  "id": "CVE-2026-23518",
  "lastModified": "2026-01-21T22:15:50.140",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 9.3,
          "baseSeverity": "CRITICAL",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "HIGH",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
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        },
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        "type": "Secondary"
      }
    ]
  },
  "published": "2026-01-21T22:15:50.140",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/fleetdm/fleet/commit/e225ef57912c8f4ac8977e24b5ebe1d9fd875257"
    },
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    }
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        {
          "lang": "en",
          "value": "CWE-347"
        }
      ],
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      "type": "Primary"
    }
  ]
}

GHSA-63M5-974W-448V

Vulnerability from github – Published: 2026-01-20 20:55 – Updated: 2026-01-22 15:39

Summary

Fleet has a JWT signature bypass vulnerability in Azure AD MDM enrollment

Details

Summary

A vulnerability in Fleet’s Windows MDM enrollment flow could allow an attacker to submit forged authentication tokens that are not properly validated. Because JWT signatures were not verified, Fleet could accept attacker-controlled identity claims, enabling enrollment of unauthorized devices under arbitrary Azure AD user identities.

Impact

If Windows MDM is enabled, an attacker can enroll rogue devices by submitting a forged JWT containing arbitrary identity claims. Due to missing JWT signature verification, Fleet accepts these claims without validating that the token was issued by Azure AD, allowing enrollment under any Azure AD user identity.

Patches

4.78.3
4.77.1
4.76.2
4.75.2
4.53.3

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 Join #fleet in osquery Slack

Credits

We thank @secfox-ai for responsibly reporting this issue.

Severity ?

9.3 (Critical)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/fleetdm/fleet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.78.0"
            },
            {
              "fixed": "4.78.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/fleetdm/fleet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.77.0"
            },
            {
              "fixed": "4.77.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/fleetdm/fleet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.76.0"
            },
            {
              "fixed": "4.76.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/fleetdm/fleet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.75.0"
            },
            {
              "fixed": "4.75.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/fleetdm/fleet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.43.5-0.20260112202845-e225ef57912c"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-23518"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-347"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-20T20:55:17Z",
    "nvd_published_at": "2026-01-21T22:15:50Z",
    "severity": "CRITICAL"
  },
  "details": "### Summary\n\nA vulnerability in Fleet\u2019s Windows MDM enrollment flow could allow an attacker to submit forged authentication tokens that are not properly validated. Because JWT signatures were not verified, Fleet could accept attacker-controlled identity claims, enabling enrollment of unauthorized devices under arbitrary Azure AD user identities.\n\n### Impact\n\nIf Windows MDM is enabled, an attacker can enroll rogue devices by submitting a forged JWT containing arbitrary identity claims. Due to missing JWT signature verification, Fleet accepts these claims without validating that the token was issued by Azure AD, allowing enrollment under any Azure AD user identity.\n\n### Patches\n\n- 4.78.3\n- 4.77.1\n- 4.76.2\n- 4.75.2\n- 4.53.3\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:\n\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 @secfox-ai for responsibly reporting this issue.",
  "id": "GHSA-63m5-974w-448v",
  "modified": "2026-01-22T15:39:04Z",
  "published": "2026-01-20T20:55:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/fleetdm/fleet/security/advisories/GHSA-63m5-974w-448v"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23518"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fleetdm/fleet/commit/e225ef57912c8f4ac8977e24b5ebe1d9fd875257"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/fleetdm/fleet"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Fleet has a JWT signature bypass vulnerability in Azure AD MDM enrollment "
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-23518 (GCVE-0-2026-23518)

FKIE_CVE-2026-23518

GHSA-63M5-974W-448V

Summary

Impact

Patches

Workarounds

For more information

Credits

Tags

Sightings

Nomenclature