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HIGH severity

CVE-2018-20321 — rancher

HIGHFix: rancher/rancher@6ea187f

CVE-2018-20321 is a high-severity (CVSS 8.8) CWE-668 vulnerability in github.com/rancher/rancher. A fix is available for github.com/rancher/rancher — see the affected versions and patch details below.

Access Control Bypass

Also known asGHSA-9qq2-xhmc-h9qrGO-2022-0644
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.8%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs77th percentile — riskier than 77% of all scored CVEsHighest risk
0.00%0.77%1.53%2.30%0.4%1.8%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2018-20321 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐹github.com/rancher/rancher

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

An issue was discovered in Rancher 2 through 2.1.5. Any project member with access to the default namespace can mount the netes-default service account in a pod, and then use that pod to execute administrative privileged commands against the k8s cluster. This could be mitigated by isolating the default namespace in a separate project, where only cluster admins can be given permissions to access. As of 2018-12-20, this bug affected ALL clusters created or imported by Rancher.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/rancher/rancher≥ 2.0.0&&< 2.1.62.1.6go get github.com/rancher/rancher@v2.1.6

Affected Products

1 product · 1 configurations
Application
ranchersuse
≥ 2.0.0 && ≤ 2.1.5
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/rancher/rancher, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/rancher/rancher to 2.1.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-20321 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

An issue was discovered in Rancher 2 through 2.1.5. Any project member with access to the default namespace can mount the netes-default service account in a pod, and then use that pod to execute administrative privileged commands against the k8s cluster. This could be mitigated by isolating the default namespace in a separate project, where only cluster admins can be given permissions to access. As of 2018-12-20, this bug affected ALL clusters created or imported by Rancher.
O3 Security · Impact-Aware SCA

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CVE-2018-20321: rancher — Fixed in 2.1.6