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Missing AuthorizationWeakness · CWE-862

CVE-2026-39910

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-08
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
STACKIT IaaS API contains a missing authorization check vulnerability that allows authenticated, low-privileged attackers to escalate privileges to full organization compromise by attaching arbitrary service accounts to virtual machines they control. Attackers can exploit the unvalidated PUT servers service-accounts endpoint to attach high-privileged service accounts and query the Instance Metadata Service to retrieve OAuth2 tokens, bypassing tenant boundaries and gaining unauthorized control over the entire organization environment.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The STACKIT IaaS API's PUT /servers/{id}/service-accounts endpoint lacks proper authorization validation, allowing authenticated low-privileged users to attach high-privileged service accounts to virtual machines they control. Attackers then query the Instance Metadata Service to retrieve OAuth2 tokens, bypassing tenant boundaries and gaining full organization-level access.

MitigationImplement and enforce proper authorization checks on the service-account attachment endpoint to validate that the requesting user has sufficient privileges to attach the specified service account, and add tenant boundary enforcement to prevent cross-tenant token retrieval.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify STACKIT IaaS API deployment
    Review your infrastructure documentation or query your cloud service inventory to confirm you are using STACKIT IaaS API services.
    Affected if STACKIT IaaS API is deployed in your environment.
  2. Check STACKT IaaS API version
    Locate the installed version of the STACKIT IaaS API service in your deployment (typically found in service metadata, container image tags, or installed package versions) and compare it against any released versions that include the fix for this authorization bypass.
    Affected if Your installed version predates the patched release that addresses the missing authorization check in the PUT servers service-accounts endpoint.
  3. Verify authorization on service-accounts endpoint
    Using a low-privilege service account that has basic VM access but lacks administrative permissions, attempt a PUT request to the /servers/{server_id}/service-accounts endpoint to attach a high-privileged service account to a controlled VM. Check if the request succeeds without returning an authorization error.
    Affected if The low-privileged user can successfully attach arbitrary service accounts to VMs they control, indicating the authorization check is missing.
  4. Inspect Instance Metadata Service exposure
    From within a VM, query the Instance Metadata Service endpoint (typically http://169.254.169.254 or equivalent) to determine if OAuth2 tokens for attached service accounts are retrievable. Verify whether tenant isolation is enforced on token retrieval.
    Affected if The Instance Metadata Service returns OAuth2 tokens for service accounts attached to the VM, and no tenant boundary checks prevent cross-tenant token retrieval.
  5. Audit service account attachments
    Review the audit logs or API access logs for the /servers/{server_id}/service-accounts endpoint to identify any attachments of high-privilege service accounts to VMs owned by low-privilege users that were not initiated by administrators.
    Affected if Service account attachments exist that were created by low-privileged users targeting high-privilege service accounts, indicating exploitation.

You are affected if your environment runs a vulnerable version of STACKIT IaaS API where low-privileged users can attach arbitrary service accounts to their VMs and retrieve OAuth2 tokens from the Instance Metadata Service, enabling cross-tenant privilege escalation.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement and enforce proper authorization checks on the service-account attachment endpoint to validate that the requesting user has sufficient privileges to attach the specified service account, and add tenant boundary enforcement to prevent cross-tenant token retrieval.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,880
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,808.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-39910 in production — separate from our analysis above.

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What this is

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