CVE
Fleet authorization bypass in user administration API
Affects Fleet versions before 4.89.0 when a user is created or modified with membership across multiple teams. Fixed in 4.89.0.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 4.89.0
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. Fleet versions before 4.89.0 A user is created or modified with membership across multiple teams Attacker must be authenticated as a team administrator
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- FIRST's estimate of the chance attackers exploit it in the next 30 days, updated daily.What do these mean? →
- 0.49% · 42nd percentile
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 17/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Fleet before 4.89.0 contains an incorrect authorization flaw in its user administration API that accepts user creation or modification when the caller administers any one of the assigned teams. Authenticated team administrators can grant users administrator roles on other teams, then deploy software and execute scripts on those teams' hosts.
Who should check
Teams running Fleet (fleetdm/fleet) before 4.89.0, especially multi-team deployments where teams are separate business units or customers.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure8/25Specific setups only, reachable over the network
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.6/10CVSS 8.6
- No patch0/5No signal
What would change the score
- Would score about 67 if added to CISA KEV
- Would score about 62 if CISA's SSVC rates exploitation active
- Would score about 24 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
Fleet versions before 4.89.0 A user is created or modified with membership across multiple teams Attacker must be authenticated as a team administratorUpgrade to a fixed version: 4.89.0.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-126402 (Fleet before 4.89.0 Broken Access Control via User Administration API), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-126402 (entry last updated 2026-11-13):
Affected:
- fleetdm fleet: fixed in 4.89.0
Fixed versions: 4.89.0.
Conditions (all must be true for the bug to be hit):
- Fleet versions before 4.89.0 (source: https://www.vulncheck.com/advisories/fleet-before-4.89.0-broken-access-control-via-user-administration-api)
- A user is created or modified with membership across multiple teams (source: https://github.com/fleetdm/fleet/security/advisories/GHSA-mj9p-fq5h-mw8h)
- Attacker must be authenticated as a team administrator (source: https://github.com/fleetdm/fleet/security/advisories/GHSA-mj9p-fq5h-mw8h)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, high-privilege login, no user action.
CISA KEV: CVE-2026-126402 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126402 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/fleetdm/fleet/security/advisories/GHSA-mj9p-fq5h-mw8h
- https://www.vulncheck.com/advisories/fleet-before-4.89.0-broken-access-control-via-user-administration-api
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-126402
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126402"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- fleetdm fleet
fixed in 4.89.0
Evidence 4
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-126402
Is CVE-2026-126402 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
A flaw in Fleet's user administration API lets a team administrator grant administrator roles on other teams. That lets them deploy software and run scripts on those teams' hosts.Source: vulncheck.com, github.com
Which versions are affected by CVE-2026-126402?
fleet: before 4.89.0.Source: cve.now feed data
Am I affected, and how do I check?
Fleet versions before 4.89.0 are affected, but only where a user was created or modified with membership across multiple teams. To check, compare your Fleet version with 4.89.0 and review whether any user accounts belong to more than one team.Source: vulncheck.com, github.com
How do I fix CVE-2026-126402?
Upgrade Fleet to 4.89.0 or later, which contains the fix.Source: vulncheck.com, github.com