Summary
Fleet has SAML authentication vulnerability due to improper SAML response validation
A vulnerability in Fleet’s SAML authentication handling could allow an attacker to forge authentication assertions and gain unauthorized access to Fleet. In certain configurations, this could result in the creation of new user accounts, including administrative accounts. This issue affects Fleet deployments using single sign-on (SSO).
Workarounds
If an immediate upgrade is not possible, Fleet users should temporarily disable single-sign-on (SSO) and use password authentication.
Credit
Thank you @hakivvi, as well as Jeffrey Hofmann and Colby Morgan from the Robinhood Red Team for finding and reporting this vulnerability using our responsible disclosure process.
For more information
If you have any questions or comments about this advisory:
- Email us at [email protected]
- Join #fleet in osquery Slack
Impact
In vulnerable versions of Fleet, an attacker could craft a specially-formed SAML response to:
- Forge authentication assertions, potentially impersonating legitimate users.
- If Just-In-Time (JIT) provisioning is enabled, the attacker could provision a new administrative user account.
- If MDM enrollment is enabled, certain endpoints could be used to create new accounts tied to forged assertions.
This could allow unauthorized access to Fleet, including administrative access, visibility into device data, and modification of configuration.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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This issue is addressed in commit fc96cc4 and is available in Fleet version 4.64.2.
The following backport versions also address this issue:
- 4.63.2
- 4.62.4
- 4.58.1
- 4.53.2
Frequently Asked Questions
- What is CVE-2025-27509? CVE-2025-27509 is a critical-severity security vulnerability in github.com/fleetdm/fleet/v4 (go), affecting versions >= 4.64.0, < 4.64.2. It is fixed in 4.64.2, 4.63.2, 4.62.4, 4.58.1, 4.53.2.
- Which versions of github.com/fleetdm/fleet/v4 are affected by CVE-2025-27509? github.com/fleetdm/fleet/v4 (go) versions >= 4.64.0, < 4.64.2 is affected.
- Is there a fix for CVE-2025-27509? Yes. CVE-2025-27509 is fixed in 4.64.2, 4.63.2, 4.62.4, 4.58.1, 4.53.2. Upgrade to this version or later.
- Is CVE-2025-27509 exploitable, and should I be worried? Whether CVE-2025-27509 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-27509 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-27509?
- Upgrade
github.com/fleetdm/fleet/v4to 4.64.2 or later - Upgrade
github.com/fleetdm/fleet/v4to 4.63.2 or later - Upgrade
github.com/fleetdm/fleet/v4to 4.62.4 or later - Upgrade
github.com/fleetdm/fleet/v4to 4.58.1 or later - Upgrade
github.com/fleetdm/fleet/v4to 4.53.2 or later
- Upgrade