CVE-2026-44936: SUSE Rancher Fleet Helm Credential Leakage Vulnerability

Technical summary

CVE-2026-44936 stems from insufficient input validation in Rancher Fleet's bundle reader. The vulnerability manifests when the helmRepoURLRegex field remains unset on a GitRepo resource, disabling the intended URL filtering mechanism for Helm repositories. The affected code path processes helm.repo entries from fleet.yaml manifests without validating whether the target URL is authorized, then automatically appends stored BasicAuth credentials when fetching from that repository. The vulnerability chain requires an actor with Git push permissions to the monitored repository—typically internal developers or CI/CD systems—to inject a malicious helm.repo URL. Upon reconciliation, Fleet forwards the credentials as HTTP Basic Authentication headers, enabling direct credential exfiltration. The issue affects multiple minor versions across the 0.12, 0.13, 0.14, and 0.15 release branches.

Business impact

Compromise of Helm repository credentials creates a supply chain risk. Attackers obtaining these credentials can push malicious Helm charts to organizations' repositories, poisoning deployments across clusters managed by that Fleet instance. In environments where Helm credentials have elevated privileges or access to internal/private chart repositories, the blast radius extends to potentially all applications deployed through affected clusters. For organizations using Helm authentication for access control, credential leakage also violates the principle of least privilege and complicates audit trails. The requirement for Git push access limits exposure to insider threats or compromised CI/CD systems, but the impact—once triggered—is organization-wide.

Affected systems

SUSE Rancher Fleet versions 0.15.0–0.15.1, 0.14.0–0.14.5, 0.13.0–0.13.10, and 0.12.0–0.12.14 are vulnerable. Patched versions are 0.15.2 and later, 0.14.6 and later, 0.13.11 and later, and 0.12.15 and later. Vulnerability is present only when helmRepoURLRegex is not explicitly configured on affected GitRepo resources—systems with this field properly set are protected. Any deployment consuming Helm charts via Fleet bundles with BasicAuth credentials is in scope if helmRepoURLRegex validation is absent.

Exploitability

Exploitation requires two conditions: Git repository push access and the absence of helmRepoURLRegex filtering. The barrier to entry is moderate. An insider developer, rogue service account, or actor who compromises a CI/CD credential can modify a fleet.yaml file to inject a Helm repository URL pointing to attacker infrastructure. No user interaction is required once the malicious configuration is committed—Fleet's automatic reconciliation triggers credential forwarding. However, the attack is not readily weaponizable by unauthenticated external attackers due to the Git access prerequisite. Organizations with strict Git access controls and immutable fleet.yaml deployments have reduced risk.

Remediation

Upgrade affected Rancher Fleet instances to patched versions: 0.15.2+, 0.14.6+, 0.13.11+, or 0.12.15+ depending on your current release line. If immediate patching is not feasible, implement helmRepoURLRegex validation on all GitRepo resources to restrict Helm repository URLs to a whitelist of approved endpoints. This control mitigates the vulnerability by preventing unapproved URLs from receiving credentials. Additionally, review Git repository access controls to limit who can push to fleet-monitored repositories, and audit recent fleet.yaml commits for unauthorized Helm repository entries.

Patch guidance

Verify the version of Rancher Fleet deployed in your environment using 'fleet -v' or by checking the Fleet controller image tag. Identify the applicable patch version for your release line and consult the SUSE advisory for detailed upgrade instructions specific to your deployment model (Rancher-managed, standalone, air-gapped). Test patches in a non-production environment first to ensure compatibility with existing fleet bundles. Upgrades may require Fleet controller restarts but typically do not mandate workload migration.

Detection guidance

Monitor Git commit history for unauthorized additions or modifications to helm.repo fields in fleet.yaml files. Log and alert on Fleet controller reconciliation events that involve Helm repository authentication, particularly those targeting unusual or external URLs. Check for outbound HTTPS connections from Fleet controllers to unexpected endpoints on ports 443. If BasicAuth credentials are logged, search logs for instances where credentials from one Helm repository appear in requests to different repositories or external hosts. Examine Git access logs to identify accounts with unexpected push activity to Fleet repositories.

Why prioritize this

This vulnerability warrants timely but non-emergency patching. The CVSS score of 5.0 (Medium) reflects the requirement for authenticated Git access, limiting broad exploitation risk. However, the credential leakage impact and supply chain implications justify prioritization above low-risk issues. Organizations with strict Git access controls and networks where Helm credentials hold significant value should prioritize patching within 60 days. Those with open Git repositories or shared CI/CD credentials should accelerate remediation to 14–30 days.

Risk score, explained

The CVSS v3.1 score of 5.0 (Medium) reflects a Low attack vector in terms of authentication required (PR:L—low privilege user needed for Git push) and a high confidence that exploitation will work (AC:L—low attack complexity). The scope is Changed (S:C), indicating the vulnerability can affect systems and users beyond the vulnerable component (e.g., downstream cluster deployments). Confidentiality impact is Low (C:L) because credentials are leaked, not the actual cluster or application data. Integrity and Availability are None because the attack does not directly modify configurations or disrupt services—the impact is credential exposure. The score does not factor in the supply chain risk, which would elevate business severity independent of the CVSS base score.

Frequently asked questions