CVE-2026-44935

Rancher Fleet vulnerable to cross namespace secret disclosure via unvalidated valuesFrom references in Helm Deployer

Workarounds

If you can't upgrade to a fixed version, please make sure that tenants do not have shared access to the same downstream clusters.

Credits

This security issue was reported by the following collaborators according to our responsible disclosure policy:

• Radisauskas Arnoldas from NATO and the NATO Cyber Security Centre (NCSC).

References

If you have any questions or comments about this advisory:

• Reach out to the SUSE Rancher Security team for security related inquiries.
• Open an issue in the Rancher repository.
• Verify with our support matrix and product support lifecycle.

A vulnerability in Fleet for Rancher Manager affects multi-tenancy environments where different tenants share the same downstream clusters (e.g., different privileged or untrusted teams inside the same organization).

On unpatched versions, tenants could bypass restrictions to access any config map or secret across all namespaces on the downstream cluster. They can create cluster-wide resources using HelmOp or Bundle without authorization.
Specifically, an attacker can exploit this vulnerability in the following ways:

1. Use valuesFrom in fleet.yaml(through a GitRepo resource) or a `HelmOp resource to read the contents of any secret an on the downstream cluster, provided they know or can guess the name, namespace, and key.
2. Deploy HelmOp and Bundle resources without being restricted to a specific service account for the Fleet agent.

If you use Fleet in a multi-tenant environment, it's recommended that you:

• Review your cluster and Fleet deployments logs for indicators of unauthorized access across tenant namespaces.
• Rotate any service accounts and credentials that might have been exposed.

Please consult the associated MITRE ATT&CK - Technique - Unsecured Credentials for further information about this category of attack.

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

CVE-2026-44935 has a CVSS score of 9.9 (Critical). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.15.2, 0.14.6, 0.13.11, 0.12.15); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

To resolve this vulnerability, upgrade to a patched version of Fleet. The new Policy resource allows you to:

• Configure GitRepos, HelmOps, and Bundles to require a specific service account for the Fleet agent on downstream clusters used for deployment. The agent uses these designated service accounts for operations, blocking access to unauthorized resources.
• Restrict HelmOp repository and chart URLs by using a regular expression. The regular expression is automatically anchored with ^ and $, meaning it must match the entire URL string.

Like GitRepoRestriction, a Policy resource must be created in the specific namespace you want to restrict, and it only applies to that namespace.

Note: Before applying a policy, ensure that the required service account is available on the downstream clusters and is configured with least-privilege permissions.

Patched versions of Fleet include releases v0.15.2, v0.14.6, 0.13.11, and v0.12.15.

1. What is CVE-2026-44935? CVE-2026-44935 is a critical-severity incorrect authorization vulnerability in github.com/rancher/fleet (go), affecting versions >= 0.15.0, < 0.15.2. It is fixed in 0.15.2, 0.14.6, 0.13.11, 0.12.15. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. How severe is CVE-2026-44935? CVE-2026-44935 has a CVSS score of 9.9 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/rancher/fleet are affected by CVE-2026-44935? github.com/rancher/fleet (go) versions >= 0.15.0, < 0.15.2 is affected.
4. Is there a fix for CVE-2026-44935? Yes. CVE-2026-44935 is fixed in 0.15.2, 0.14.6, 0.13.11, 0.12.15. Upgrade to this version or later.
5. Is CVE-2026-44935 exploitable, and should I be worried? Whether CVE-2026-44935 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44935 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44935?
   • Upgrade github.com/rancher/fleet to 0.15.2 or later
   • Upgrade github.com/rancher/fleet to 0.14.6 or later
   • Upgrade github.com/rancher/fleet to 0.13.11 or later
   • Upgrade github.com/rancher/fleet to 0.12.15 or later

Other vulnerabilities in github.com/rancher/fleet