How severe is CVE-2025-27509?

No CVSS score has been assigned to CVE-2025-27509 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-27509?

CVE-2025-27509 affects the following packages: github.com/fleetdm/fleet/v4 (Go), github.com/fleetdm/fleet/v4 (Go), github.com/fleetdm/fleet/v4 (Go), github.com/fleetdm/fleet/v4 (Go), github.com/fleetdm/fleet/v4 (Go). Ecosystems affected: Go.

How do I fix CVE-2025-27509?

Update github.com/fleetdm/fleet/v4 to 4.64.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-27509 is resolved across your whole dependency graph.

How do I detect CVE-2025-27509 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/fleetdm/fleet/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-27509 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2025-27509?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-27509 can be triaged on real exposure rather than presence alone.

Is CVE-2025-27509 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-27509 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-27509?

CVE-2025-27509 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 50th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-27509?

CVE-2025-27509 is classified as CWE-285 (CWE-285). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-27509 published, and has it been updated?

CVE-2025-27509 was published on March 6, 2025 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2025-27509 — v4

Fix: fleetdm/fleet@718c95e

CVE-2025-27509 is a CWE-285 vulnerability in github.com/fleetdm/fleet/v4. A fix is available for github.com/fleetdm/fleet/v4 — see the affected versions and patch details below.

SAML authentication vulnerability due to improper SAML response validation

Also known asGHSA-52jx-g6m5-h735GO-2025-3505

Published

Mar 6, 2025

Updated

Aug 12, 2026

Affected

5 pkgs

Patched

5 / 5

Exploits

None indexed

Exploitation data as of Sep 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-27509.

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs50th percentile — riskier than 50% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

5 pkgs affected

🐹github.com/fleetdm/fleet/v4🐹github.com/fleetdm/fleet/v4🐹github.com/fleetdm/fleet/v4🐹github.com/fleetdm/fleet/v4🐹github.com/fleetdm/fleet/v4

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

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).

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.

Patches

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

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

Affected Packages

5 total 5 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/fleetdm/fleet/v4`	≥ 4.64.0&&< 4.64.2	4.64.2`go get github.com/fleetdm/fleet/v4@v4.64.2`
🐹Go	`github.com/fleetdm/fleet/v4`	≥ 4.63.0&&< 4.63.2	4.63.2`go get github.com/fleetdm/fleet/v4@v4.63.2`
🐹Go	`github.com/fleetdm/fleet/v4`	≥ 4.62.0&&< 4.62.4	4.62.4`go get github.com/fleetdm/fleet/v4@v4.62.4`
🐹Go	`github.com/fleetdm/fleet/v4`	≥ 4.54.0&&< 4.58.1	4.58.1`go get github.com/fleetdm/fleet/v4@v4.58.1`
🐹Go	`github.com/fleetdm/fleet/v4`	all versions	4.53.2`go get github.com/fleetdm/fleet/v4@v4.53.2`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/fleetdm/fleet/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/fleetdm/fleet/v4 to 4.64.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-27509 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-27509 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2025-27509. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary 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). ### 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 c

O3 Security · Impact-Aware SCA

Is CVE-2025-27509 in your dependencies?

O3 Security finds CVE-2025-27509 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works

CVE-2025-27509 — v4

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

Real-World Exposure

Description

Summary

Impact

Patches

Workarounds

Credit

For more information

Affected Packages

Detection & mitigation playbook

Detect

Fix

Workarounds

How O3 protects you

Frequently Asked Questions

Is CVE-2025-27509 in your dependencies?