How severe is GHSA-4f9r-x588-pp2h?

No CVSS score has been assigned to GHSA-4f9r-x588-pp2h yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-4f9r-x588-pp2h?

GHSA-4f9r-x588-pp2h affects the following packages: github.com/fleetdm/fleet/v4 (Go). Ecosystems affected: Go.

How do I fix GHSA-4f9r-x588-pp2h?

Update github.com/fleetdm/fleet/v4 to 4.81.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4f9r-x588-pp2h is resolved across your whole dependency graph.

How do I detect GHSA-4f9r-x588-pp2h 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 GHSA-4f9r-x588-pp2h if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is GHSA-4f9r-x588-pp2h actively exploited in the wild?

No public exploit code has been indexed for GHSA-4f9r-x588-pp2h 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 GHSA-4f9r-x588-pp2h?

GHSA-4f9r-x588-pp2h has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 9th 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 GHSA-4f9r-x588-pp2h?

GHSA-4f9r-x588-pp2h is classified as Improper Authentication (CWE-287). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-4f9r-x588-pp2h published, and has it been updated?

GHSA-4f9r-x588-pp2h was published on March 30, 2026 and was last updated on April 2, 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

Fleet's user account creation via invite does not enforce invited email addressGHSA-4f9r-x588-pp2h

GHSA-4f9r-x588-pp2h is a Improper Authentication 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.

Also known asCVE-2026-34389GO-2026-4912

Published

Mar 30, 2026

Updated

Apr 2, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 10, 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.
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 GHSA-4f9r-x588-pp2h.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs9th percentile — riskier than 9% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹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

Fleet contained an issue in the user invitation flow where the email address provided during invite acceptance was not validated against the email address associated with the invite. An attacker who obtained a valid invite token could create an account under an arbitrary email address while inheriting the role granted by the invite, including global admin.

Impact

If an attacker gains access to a valid invite token, they can create a Fleet user account with an email address of their choosing while inheriting the invite’s assigned role and team memberships.

This issue:

Requires possession of a valid invite token
Does not bypass authentication controls beyond invite-based account creation
Does not expose data without successful account creation

Workarounds

If upgrading immediately is not possible:

Treat invite links as sensitive credentials and avoid sharing them in public or semi-public channels (e.g., Slack, Teams).
Revoke and reissue invites if there is any concern that an invite link may have been exposed.
Prefer issuing invites with the minimum required privileges and elevating roles after account creation when appropriate.

For more information

If there are any questions or comments about this advisory:

Send an email to [email protected]

Credits

Fleet thanks @fuzzztf for responsibly reporting this issue.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/fleetdm/fleet/v4`	all versions	4.81.0`go get github.com/fleetdm/fleet/v4@v4.81.0`

Affected Products

1 product · 1 configurations

Application

fleetfleetdm

< 4.81.1

range

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 4.81.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4f9r-x588-pp2h is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### Summary Fleet contained an issue in the user invitation flow where the email address provided during invite acceptance was not validated against the email address associated with the invite. An attacker who obtained a valid invite token could create an account under an arbitrary email address while inheriting the role granted by the invite, including global admin. ### Impact If an attacker gains access to a valid invite token, they can create a Fleet user account with an email address of their choosing while inheriting the invite’s assigned role and team memberships. This issue: - Req

O3 Security · Impact-Aware SCA

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Fleet's user account creation via invite does not enforce invited email addressGHSA-4f9r-x588-pp2h

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

Real-World Exposure

Description

Summary

Impact

Workarounds

For more information

Credits

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is GHSA-4f9r-x588-pp2h in your dependencies?