Rancher Fleet’s bundle reader lacks input validation when the helmRepoURLRegex field is not set on a GitRepo resource, creating a Server Side Request Forgery weakness (CWE‑918). This bug allows an attacker who can push to a Fleet‑managed Git repository to insert an arbitrary URL into the helm.repo field of a fleet.yaml file. During normal operation, Fleet forwards Helm authentication credentials (BasicAuth) to the specified URL, resulting in those credentials being transmitted to an attacker‑controlled endpoint. The vulnerability does not provide arbitrary code execution; its primary impact is the leakage of privileged Helm repository credentials that could be used to access or modify downstream resources.

SUSE Rancher Fleet versions 0.15.x up to and including 0.15.1, 0.14.x up to and including 0.14.5, 0.13.x up to and including 0.13.10, and 0.12.x up to and including 0.12.14 are affected by this issue.

The CVSS score of 5 reflects moderate severity, and the EPSS score of less than 1% indicates a low current probability of exploitation. This vulnerability is not listed in the CISA KEV catalog. Exploitation requires the attacker to have write access to a Fleet‑monitored Git repository. Once that condition is met, the attacker can create or modify a fleet.yaml file to set an arbitrary helm.repo URL, causing Fleet to send its BasicAuth credentials to the attacker’s endpoint. The exploitation path is relatively straightforward and does not require privileged access beyond the ability to write to the repository.