CVE-2026-41050: Fleet Helm Impersonation Bypass Of `RESTClientGetter` Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-765j-qfrp-hm3j",
  "modified" : "2026-05-14T20:31:35Z",
  "published" : "2026-05-07T01:26:06Z",
  "aliases" : [ "CVE-2026-41050" ],
  "summary" : "Fleet: Helm impersonation bypass of `RESTClientGetter` retains `cluster-admin` during template rendering",
  "details" : "### Impact\n\nFleet's Helm deployer did not fully apply ServiceAccount impersonation in two code paths, allowing a tenant with git push access to a Fleet-monitored repository to read secrets from any namespace on every downstream cluster targeted by their `GitRepo`.\n\n**Helm `lookup` bypass:** The Helm template engine ran Kubernetes API queries with the fleet-agent's cluster-admin credentials instead of the impersonated ServiceAccount. A chart template could therefore access resources beyond the tenant's RBAC scope.\n\n**`valuesFrom` bypass:** Secret and ConfigMap references in `fleet.yaml` `helm.valuesFrom` were read using the fleet-agent's cluster-admin client. A tenant could reference resources in namespaces the impersonated ServiceAccount has no access to.\nBoth issues break Fleet's multi-tenant impersonation boundary. The leaked credentials may belong to external services, making the full impact non-deterministic.\nSingle-tenant deployments where all users are trusted are not affected.\n\n**Important:**\n- For the exposure of additional credentials, the final impact severity for confidentiality, integrity and availability is dependent on the permissions the leaked credentials have on their services.\n- It is recommended to review for potentially leaked credentials in this scenario and to change them if deemed necessary.\n\nPlease consult the associated  [MITRE ATT&CK - Technique - Account Access Removal](https://attack.mitre.org/techniques/T1531/) for further information about this category of attack.\n\n### Patches\n\nBoth issues are fixed by ensuring the Helm action configuration consistently uses the impersonated ServiceAccount credentials throughout all Helm operations.\n\nPatched versions of Rancher include releases `v2.14.1`, `v2.13.5`, `v2.12.9`, and `v2.11.13`. For Rancher `v2.10.11`, users must manually update their Fleet deployment to version`v0.11.13`.\n\n### Workarounds\n\nNo workaround fully mitigates the issue for multi-tenant deployments. The patches should be applied as soon as they are available.\n\nThe following measures reduce the attack surface but do not close either vulnerability:\n\n- Restrict git push access to Fleet-monitored repositories to trusted users only. In a multi-tenant setup this removes the precondition entirely, but is often not operationally viable.\n- Use `GitRepoRestriction` resources to limit which ServiceAccounts each namespace is allowed to use, restricting the set of users who can configure impersonation at all.\n- Audit deployed chart templates for `lookup` calls and `fleet.yaml` files for cross-namespace `valuesFrom` references as a detective control.\n\n### Resources\n\nIf there are any questions or comments about this advisory:\n\n- Reach out to the [SUSE Rancher Security team](https://github.com/rancher/rancher/security/policy) for security related inquiries.\n- Open an issue in the [Rancher](https://github.com/rancher/rancher/issues/new/choose) repository.\n- Verify using the [support matrix](https://www.suse.com/suse-rancher/support-matrix/all-supported-versions/) and [product support lifecycle](https://www.suse.com/lifecycle/).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/rancher/fleet"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.15.0"
      }, {
        "fixed" : "0.15.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/rancher/fleet"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.14.0"
      }, {
        "fixed" : "0.14.5"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/rancher/fleet"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.13.0"
      }, {
        "fixed" : "0.13.10"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/rancher/fleet"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.12.0"
      }, {
        "fixed" : "0.12.14"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/rancher/fleet"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.11.0"
      }, {
        "fixed" : "0.11.13"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/rancher/fleet/security/advisories/GHSA-765j-qfrp-hm3j"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-41050"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.suse.com/show_bug.cgi?id=CVE-2026-41050"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rancher/fleet"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-863" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-07T01:26:06Z",
    "nvd_published_at" : "2026-05-13T08:16:16Z"
  }
}