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CVE-2026-41050 critical CVSS 9.9

Authorization Flaw in github.com/rancher/fleet (CVE-2026-41050)

Summary

Vulnerability in github.com/rancher/fleet (CVE-2026-41050). Successful exploitation can lead to full system takeover. Exploitable via GitRepo. Mitigation: upgrade to 0.11.13 or later.

Original description

The description as published by the source.

Impact

Fleet'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.

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.

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.
Both issues break Fleet's multi-tenant impersonation boundary. The leaked credentials may belong to external services, making the full impact non-deterministic.
Single-tenant deployments where all users are trusted are not affected.

Important:

  • 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.
  • It is recommended to review for potentially leaked credentials in this scenario and to change them if deemed necessary.

Please consult the associated MITRE ATT&CK - Technique - Account Access Removal for further information about this c…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-41050 has been found in github.com/rancher/fleet.
Attackers can target a specific entry point like GitRepo over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 9.9/10.
What to do: upgrade github.com/rancher/fleet to 0.11.13 or later.
If unsure, ask your IT team or search "github.com/rancher/fleet CVE-2026-41050" on the vendor's site.

CVE-2026-41050 (github.com/rancher/fleet) — CWE-863 / CVSS v3 9.9
Attack vector: remote (network-reachable) / no user interaction
Attack surface: GitRepo / lookup / valuesFrom / fleet.yaml
Patched: 0.11.13 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Incorrect authorization (CWE-863) exists in github.com/rancher/fleet. Attackers reach the vulnerable code path via GitRepo.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/rancher/fleet. Attack surface: GitRepo / lookup / valuesFrom / fleet.yaml.

🔥 Severity

Severity: Critical (CVSS 9.9/10). Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 0.11.13.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/rancher/fleet' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'github.com/rancher/fleet' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で github.com/rancher/fleet を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade github.com/rancher/fleet to 0.11.13

    ステージング環境で 0.11.13 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

go github.com/rancher/fleet
[{"type":"SEMVER","events":[{"introduced":"0.11.0"},{"fixed":"0.11.13"}]}]

References

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