Skip to content
Patch Next
Sign inAdd to your agent

← Actionable
Critical, CVSS 9.3

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

CVE-2026-23518GHSA-63m5-974w-448v

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/fleetdm/fleet 4.78.3, 4.77.1, 4.76.2, 4.75.2, 4.43.5-0.20260112202845-e225ef57912c), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

Add to your agent

Affected packages

  • Go github.com/fleetdm/fleet

    Affected
    >= 4.78.0, < 4.78.3>= 4.77.0, < 4.77.1>= 4.76.0, < 4.76.2>= 4.75.0, < 4.75.2< 4.43.5-0.20260112202845-e225ef57912c
    Fixed in
    4.43.5-0.20260112202845-e225ef57912c, 4.75.2, 4.78.3, 4.77.1, 4.76.2

Sources

  • GitHub Advisory Database and maintainer security advisories on GitHub

    GitHub-reviewed advisory GHSA-63m5-974w-448v lists affected ranges: Go github.com/fleetdm/fleet >=4.78.0 =4.77.0 =4.76.0 =4.75.0 =0 <4.43.5-0.20260112202845-e225ef57912c

    VerifiedObserved Structured GitHub Advisory Database record (type=reviewed) from the GitHub REST API.

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
9.3 · 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 · score source
EPSS
  • CVE-2026-23518: 0.25% estimated exploitation activity in the next 30 days; percentile 17.07 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-63m5-974w-448v

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-23518

Advisory: Fleet has a JWT signature bypass vulnerability in Azure AD MDM enrollment
IDs: CVE-2026-23518, GHSA-63m5-974w-448v
Record: https://patchnext.com/advisories/cve-2026-23518 (revision 1, source checked 26 Oct 2026, 15:18 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/fleetdm/fleet 4.78.3, 4.77.1, 4.76.2, 4.75.2, 4.43.5-0.20260112202845-e225ef57912c. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/fleetdm/fleet: affected >= 4.78.0, < 4.78.3; >= 4.77.0, < 4.77.1; >= 4.76.0, < 4.76.2; >= 4.75.0, < 4.75.2; < 4.43.5-0.20260112202845-e225ef57912c; fixed in 4.43.5-0.20260112202845-e225ef57912c, 4.75.2, 4.78.3, 4.77.1, 4.76.2

## Suggested inspection (read-only)
- Go github.com/fleetdm/fleet: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/fleetdm/fleet.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-63m5-974w-448v (GitHub-reviewed advisory GHSA-63m5-974w-448v lists affected ranges: Go github.com/fleetdm/fleet >=4.78.0 =4.77.0 =4.76.0 =4.75.0 =0 <4.43.5-0.20260112202845-e225ef57912c)

Commands are suggestions: review each one before running it.

Loading voting…