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HIGH severity

CVE-2021-36776 — rancher

HIGH

CVE-2021-36776 is a high-severity (CVSS 8.8) CWE-284 vulnerability in github.com/rancher/rancher. A fix is available for github.com/rancher/rancher — see the affected versions and patch details below.

Rancher's Steve API Component Improper authorization check allows privilege escalation

Also known asGHSA-gvh9-xgrq-r8hwGO-2024-2771
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.1%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs66th percentile — riskier than 66% of all scored CVEsHighest risk
0.03%0.56%1.09%1.62%0.5%1.1%May 26Sep 26Nov 26

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

How urgent is this, really

Where this sits among everything scored

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

Impact

A flaw discovered in Rancher versions from 2.5.0 up to and including 2.5.9 allows an authenticated user to impersonate any user on a cluster through the Steve API proxy, without requiring knowledge of the impersonated user's credentials. This is due to the Steve API proxy not dropping the impersonation header before sending the request to the Kubernetes API. A malicious user with authenticated access to Rancher could use this to impersonate another user with administrator access in Rancher, receiving, then, administrator level access in the cluster.

Patches

Patched versions include releases 2.5.10, 2.6.0 and later versions.

Workarounds

Limit access in Rancher to trusted users. There is not a direct mitigation besides upgrading to the patched Rancher versions.

For more information

If you have any questions or comments about this advisory:

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/rancher/rancher≥ 2.5.0&&< 2.5.102.5.10go get github.com/rancher/rancher@v2.5.10

Affected Products

1 product · 1 configurations
Application
rancherrancher
< 2.5.10
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 2.5.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-36776 is resolved across your whole dependency graph.

  3. Workarounds

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### Impact A flaw discovered in Rancher versions from 2.5.0 up to and including 2.5.9 allows an authenticated user to impersonate any user on a cluster through the Steve API proxy, without requiring knowledge of the impersonated user's credentials. This is due to the Steve API proxy not dropping the impersonation header before sending the request to the Kubernetes API. A malicious user with authenticated access to Rancher could use this to impersonate another user with administrator access in Rancher, receiving, then, administrator level access in the cluster. ### Patches Patched versions in
O3 Security · Impact-Aware SCA

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CVE-2021-36776: rancher — Fixed in 2.5.10