CVE-2026-34389: Github.com/fleetdm/fleet/v4 Remote Code Execution Vulnerability

MODERATE
Advisory Identifier: GHSA-4f9r-x588-pp2h
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CWE-287
Published
Advisory Summary

CVE-2026-34389 is a MODERATE remote code execution vulnerability (CWE-287: Improper Authentication) affecting Github.com/fleetdm/fleet/v4 libraries in the Go ecosystem. The issue involves fleet's user account creation via invite does not enforce invited email address. Remediation is available by upgrading affected packages to version 4.81.0.

CVE-2026-34389 at a Glance

CVE Identifier CVE-2026-34389
GHSA Identifier GHSA-4f9r-x588-pp2h
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-287: Improper Authentication
Affected Product Github.com/fleetdm/fleet/v4
Package Ecosystem Go
Published Date
Last Updated

How to Fix CVE-2026-34389

To remediate this vulnerability, upgrade all affected Github.com/fleetdm/fleet/v4 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/fleetdm/fleet/v4 fixed: 4.81.0 
Upgrade github.com/fleetdm/fleet/v4 to 4.81.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/fleetdm/fleet/v4

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-34389, inspect your project dependencies for Github.com/fleetdm/fleet/v4:

inspect dependencies for github.com/fleetdm/fleet/v4

Analyze the terminal output to locate any version of Github.com/fleetdm/fleet/v4 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.81.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-287: Improper Authentication, where when an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. In Github.com/fleetdm/fleet/v4, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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 [security@fleetdm.com](mailto:security@fleetdm.com) ### Credits Fleet thanks @fuzzztf for responsibly reporting this issue.

CVE-2026-34389 Affected Github.com/fleetdm/fleet/v4 Versions

1 component(s)
Fixed Versions:
4.81.0
Product / Package Ecosystem Affected Versions Fixed Version
github.com/fleetdm/fleet/v4
golang/github.com/fleetdm/fleet/v4
Go
< 4.81.0
4.81.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/fleetdm/fleet/security/advisories/GHSA-4f9r-x588-pp2h
NVD — CVE-2026-34389 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-34389
Github.com/fleetdm/fleet/v4 Source Repository REPOSITORY
https://github.com/fleetdm/fleet

Frequently Asked Questions

What is CVE-2026-34389?
CVE-2026-34389 is a security vulnerability in Github.com/fleetdm/fleet/v4 involving Fleet's user account creation via invite does not enforce invited email address under CWE-287: Improper Authentication.
Which Github.com/fleetdm/fleet/v4 versions are affected?
Affected versions include releases prior to 4.81.0 across affected packages: github.com/fleetdm/fleet/v4.
What version fixes CVE-2026-34389?
Upgrading to 4.81.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/fleetdm/fleet/v4 affected?
Yes, github.com/fleetdm/fleet/v4 is affected in releases prior to 4.81.0. Upgrade your dependency to 4.81.0 or later.
What CWE is associated with CVE-2026-34389?
CVE-2026-34389 is classified under CWE-287: Improper Authentication (When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.).
How can I check Go dependencies for CVE-2026-34389?
Run the dependency tree command: 'inspect dependencies for github.com/fleetdm/fleet/v4'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4f9r-x588-pp2h",
  "modified" : "2026-03-30T19:29:13Z",
  "published" : "2026-03-30T19:29:13Z",
  "aliases" : [ "CVE-2026-34389" ],
  "summary" : "Fleet's user account creation via invite does not enforce invited email address",
  "details" : "### Summary\n\nFleet 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.\n\n### Impact\n\nIf 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.\n\nThis issue:\n\n- Requires possession of a valid invite token\n- Does not bypass authentication controls beyond invite-based account creation\n- Does not expose data without successful account creation\n\n### Workarounds\n\nIf upgrading immediately is not possible:\n\n- Treat invite links as sensitive credentials and avoid sharing them in public or semi-public channels (e.g., Slack, Teams).\n- Revoke and reissue invites if there is any concern that an invite link may have been exposed.\n- Prefer issuing invites with the minimum required privileges and elevating roles after account creation when appropriate.\n\n### For more information\n\nIf there are any questions or comments about this advisory:\n\nSend an email to [security@fleetdm.com](mailto:security@fleetdm.com)\n\n### Credits\n\nFleet thanks @fuzzztf for responsibly reporting this issue.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/fleetdm/fleet/v4"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.81.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/fleetdm/fleet/security/advisories/GHSA-4f9r-x588-pp2h"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-34389"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/fleetdm/fleet"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-30T19:29:13Z",
    "nvd_published_at" : "2026-03-27T20:16:35Z"
  }
}