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TectonicApplication · Redhat

CVE-2018-5256

HIGH · 7.5 CVSS v3.1 Published 2018-05-18
Fix available
A fix is available. Upgrade to 1.7.9-tectonic.4 / 1.8.4-tectonic.3 or later.
See remediation →
84/100
Remediation priority · High
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
CoreOS Tectonic 1.7.x before 1.7.9-tectonic.4 and 1.8.x before 1.8.4-tectonic.3 mounts a direct proxy to the kubernetes cluster at /api/kubernetes/ which is accessible without authentication to Tectonic and allows an attacker to directly connect to the kubernetes API server. Unauthenticated users are able to list all Namespaces through the Console, resulting in an information disclosure. Tectonic's exposure of an unauthenticated API endpoint containing information regarding the internal state of the cluster can provide an attacker with information that may assist in other attacks against the cluster. For example, an attacker may not have the permissions required to list all namespaces in the cluster but can instead leverage this vulnerability to enumerate the namespaces and then begin to check each namespace for weak authorization policies that may allow further escalation of privileges.

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

CoreOS Tectonic versions 1.7.x before 1.7.9-tectonic.4 and 1.8.x before 1.8.4-tectonic.3 expose an unauthenticated API endpoint at /api/kubernetes/ that proxies directly to the Kubernetes API server, allowing any unauthenticated user to list all cluster namespaces and gather internal cluster state information.

MitigationUpgrade Tectonic to version 1.7.9-tectonic.4 or 1.8.4-tectonic.3 or later to remediate the authentication bypass on the /api/kubernetes/ endpoint.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
TectonicApplication
Affected:>= 1.7.1-tectonic.1, < 1.7.9-tectonic.4>= 1.8.4-tectonic.1, < 1.8.4-tectonic.3

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
None
Availability
None

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

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 Tectonic version
    Locate the installed Tectonic version from the Tectonic console, cluster configuration, or by querying the tectonic-operator. Compare the version string to the affected ranges: 1.7.1-tectonic.1 through 1.7.9-tectonic.3, or 1.8.4-tectonic.1 through 1.8.4-tectonic.2.
    Affected if The installed version falls within the affected ranges and has not been upgraded to 1.7.9-tectonic.4 or later, or 1.8.4-tectonic.3 or later.
  2. Verify /api/kubernetes/ endpoint exists
    Attempt to access the /api/kubernetes/ endpoint on the Tectonic ingress or API server (e.g., curl https://<tectonic-host>/api/kubernetes/).
    Affected if The endpoint returns an HTTP response instead of a 404, indicating it is exposed.
  3. Test unauthenticated access to cluster namespaces
    Send a GET request to /api/kubernetes/api/v1/namespaces without providing any authentication token or credentials.
    Affected if The request returns a list of namespaces or other cluster state information without requiring authentication.

The environment is affected if the Tectonic version is in the affected range AND the /api/kubernetes/ endpoint is accessible without authentication, allowing enumeration of cluster namespaces.

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
Upgrade available Upgrade to 1.7.9-tectonic.4 / 1.8.4-tectonic.3 or later
Fixed in 1.7.9-tectonic.41.8.4-tectonic.3
Interim mitigation

Upgrade Tectonic to version 1.7.9-tectonic.4 or 1.8.4-tectonic.3 or later to remediate the authentication bypass on the /api/kubernetes/ endpoint.

Fix this in Tectonic Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,984.

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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-2018-5256 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data