---
title: "CVE-2025-27509: Fleet has SAML authentication vulnerability due to improper SAML response validation"
url: https://erroneo.us/security/cve/CVE-2025-27509/
description: "CVE-2025-27509 (github.com/fleetdm/fleet/v4 (Go)): fleetdm/fleet is an open source device management, built on osquery. In vulnerable versions of Fleet, an…"
type: vulnerability-record
section: "Security Digest"
date_published: 2025-03-06
date_modified: 2026-01-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2025-27509"
kev: false
cvss: 9.3
epss: 0.00669
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2025-27509: Fleet has SAML authentication vulnerability due to improper SAML response validation

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.7% , percentile 51: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 51% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes github.com/fleetdm/fleet/v4 (Go) >= 4.64.0, < 4.64.2, fixed in 4.64.2 ; github.com/fleetdm/fleet/v4 (Go) >= 4.63.0, < 4.63.2, fixed in 4.63.2 ; github.com/fleetdm/fleet/v4 (Go) >= 4.62.0, < 4.62.4, fixed in 4.62.4 ; github.com/fleetdm/fleet/v4 (Go) >= 4.54.0, < 4.58.1, fixed in 4.58.1 . Check your lockfile, including transitive dependencies.

## What it is

fleetdm/fleet is an open source device management, built on osquery. In vulnerable versions of Fleet, an attacker could craft a specially-formed SAML response to forge authentication assertions, provision a new administrative user account if Just-In-Time (JIT) provisioning is enabled, or create new accounts tied to forged assertions if f MDM enrollment is enabled. This vulnerability is fixed in 4.64.2, 4.63.2, 4.62.4, and 4.58.1.

## Affected packages

- Go `github.com/fleetdm/fleet/v4` >= 4.64.0, < 4.64.2 → fixed: 4.64.2
- Go `github.com/fleetdm/fleet/v4` >= 4.63.0, < 4.63.2 → fixed: 4.63.2
- Go `github.com/fleetdm/fleet/v4` >= 4.62.0, < 4.62.4 → fixed: 4.62.4
- Go `github.com/fleetdm/fleet/v4` >= 4.54.0, < 4.58.1 → fixed: 4.58.1
- Go `github.com/fleetdm/fleet/v4` < 4.53.2 → fixed: 4.53.2

## Affected products (CVE record)

- fleetdm fleet: >= 4.64.0, < 4.64.2, >= 4.63.0, < 4.63.2, >= 4.62.0, < 4.62.4, < 4.58.1

## Severity

- GitHub_M CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`
- GitHub CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.67% probability of exploitation activity in the next 30 days; percentile 51.

## Sources

- [GitHub Advisory GHSA-52jx-g6m5-h735](https://github.com/advisories/GHSA-52jx-g6m5-h735)
- [CVE.org record CVE-2025-27509](https://www.cve.org/CVERecord?id=CVE-2025-27509)
- [NVD entry CVE-2025-27509](https://nvd.nist.gov/vuln/detail/CVE-2025-27509)
- [github.com](https://github.com/fleetdm/fleet/security/advisories/GHSA-52jx-g6m5-h735)
- [github.com](https://github.com/fleetdm/fleet/commit/718c95e47ad010ad6b8ceb3f3460e921fbfc53bb)
- [github.com](https://github.com/fleetdm/fleet/releases/tag/fleet-v4.64.2)
- [pkg.go.dev](https://pkg.go.dev/vuln/GO-2025-3505)

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Source page: https://erroneo.us/security/cve/CVE-2025-27509/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt