Executive brief
Fleet is a Kubernetes deployment management tool used to manage applications across multiple clusters. An attacker who can provide content to a Git repository used by Fleet can exploit Helm template processing to leak sensitive cluster metadata and network information through DNS name resolution. Although the leaked data is limited and availability/integrity are not affected, this could reveal sensitive information in restricted network environments.
Technical details
This vulnerability is a Server-Side Request Forgery (SSRF) vulnerability in Fleet's Helm template preprocessing logic. An authenticated user with write access to a Git repository referenced by a GitRepo resource can craft malicious Helm template values that trigger network requests during template evaluation by the Fleet controller. The vulnerability allows disclosure of cluster metadata available in the templating context and information about hosts reachable from the controller's network position via DNS resolution. Exploitation requires that the repository bundle use Helm template values and that write access extend beyond trusted administrators. The fix rejects bundles whose Helm template values require network access, causing affected GitRepo resources to report errors during targeting. Patches are available in v0.12.19, v0.13.15, v0.14.10, v0.15.6, and v0.16.1.
Affected products
- Rancher Fleet 0.12.0 before 0.12.19, 0.13.0 before 0.13.15, 0.14.0 before 0.14.10, 0.15.0 before 0.15.6, 0.16.0 before 0.16.1
Timeline
- 2026-08-28: disclosed
- 2026-09-03: patched