What is CVE-2018-5256?

CVE-2018-5256 is a high-severity vulnerability in Red Hat Tectonic, classified under Information Disclosure. CVSS score: 7.5/10. Published 2018-05-18.

How severe is CVE-2018-5256?

High severity. CVSS v3 base score is 7.5 out of 10.

Is CVE-2018-5256 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Information disclosure in Red Hat Tectonic

CVE-2018-5256

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.

Vulnerability class: Information Disclosure

Published 2018-05-18 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.017 (75.9th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 76th percentile — 75.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.017 · newest: 0.017 · change: 0.000

Affected products

Red Hat Tectonic

Weakness classification (CWE)

CWE-200 — Information Disclosure

Public proof-of-concept exploits

Eriner/eriner

References

coreos.com/blog/tectonic-namespace-information-disclosure-vulnerability-patched (Vendor Advisory)
coreos.com/tectonic/releases/ (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2018-5256?: CVE-2018-5256 is a high-severity vulnerability in Red Hat Tectonic, classified under Information Disclosure. CVSS score: 7.5/10. Published 2018-05-18.
How severe is CVE-2018-5256?: High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2018-5256 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.