CVE-2026-41050: Rancher Fleet Helm impersonation bypass in RESTClientGetter

CVE-2026-41050 · Severity: critical · CVSS 9.9 · Published 2026-05-13

Rancher Fleet, a tool for managing large-scale Kubernetes cluster deployments, contains a vulnerability that allows users in a multi-tenant environment to bypass security boundaries. An attacker with the ability to push code to a monitored repository can exploit this to read sensitive secrets and configuration data from any namespace across all managed clusters. This could lead to a total compromise of the managed infrastructure and any external services whose credentials are stored within the clusters.

Technologies: github.com/rancher/fleet (Go), Suse Fleet. Vendors: Go, Suse.

Quick answers

Is CVE-2026-41050 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-41050 being exploited in the wild.
How severe is CVE-2026-41050?
Critical severity, with a CVSS score of 9.9, published 13 May 2026.
Which products and versions are affected?
github.com/rancher/fleet (Go) SEMVER:introduced=0.11.0,fixed=0.11.13,introduced=0.12.0,fixed=0.12.14,introduced=0.13.0,fixed=0.13.10,introduced=0.14.0,fixed=0.14.5,introduced=0.15.0,fixed=0.15.1, SEMVER:introduced=0.15.0,fixed=0.15.1; Suse Fleet >= 0.15.0, < 0.15.1; >= 0.14.0, < 0.14.5; >= 0.13.0, < 0.13.10; >= 0.12.0, < 0.12.14; >= 0.11.0, < 0.11.13.
Is there a fix for CVE-2026-41050?
Yes. github.com/rancher/fleet (Go): upgrade to 0.15.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-41050 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-41050?
Check whether you run github.com/rancher/fleet (Go) or Suse Fleet at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/rancher/fleet (Go): upgrade to 0.15.1 or later
    go get github.com/rancher/fleet@v0.15.1

Technical details

Rancher Fleet's Helm deployer fails to consistently apply ServiceAccount impersonation in two specific code paths: the Helm `lookup` function and the `valuesFrom` directive in `fleet.yaml`. In both cases, the system defaults to using the `fleet-agent`'s high-privilege `cluster-admin` credentials instead of the restricted tenant ServiceAccount. An attacker with 'git push' access to a Fleet-monitored repository can craft malicious Helm charts or configuration files to query the Kubernetes API or reference Secrets and ConfigMaps in unauthorized namespaces. This effectively breaks the multi-tenant isolation boundary, allowing for cross-namespace data exfiltration. The issue is resolved by ensuring the `RESTClientGetter` and Helm action configurations strictly use the impersonated credentials.

Affected products

  • Rancher Fleet >= 0.15.0, < 0.15.1; >= 0.14.0, < 0.14.5; >= 0.13.0, < 0.13.10; >= 0.12.0, < 0.12.14; >= 0.11.0, < 0.11.13

Identifiers

  • CVE-2026-41050
  • GHSA-765j-qfrp-hm3j
  • GO-2026-5207

Timeline

  • 2026-04-30: disclosed: Initial disclosure to rancher/fleet
  • 2026-05-07: advisory: GitHub Advisory published

References

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