CVE-2026-44939: Rancher vulnerable to command injection through unsanitized YAML parameter

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 1.3%, percentile 70: FIRST’s model estimates a 1.3% chance of exploitation activity in the next 30 days, higher than 70% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Only applies if your dependency tree includes github.com/rancher/rancher (Go) >= 2.14.0, < 2.14.2, fixed in 2.14.2; github.com/rancher/rancher (Go) >= 2.13.0, < 2.13.6, fixed in 2.13.6; github.com/rancher/rancher (Go) >= 2.12.0, < 2.12.10, fixed in 2.12.10; github.com/rancher/rancher (Go) >= 2.11.0, < 2.11.14, fixed in 2.11.14. Check your lockfile, including transitive dependencies.

What it is

A command injection vulnerability in the Rancher Manager cluster before 2.14.2 import endpoint /v3/import/{token}{clusterId}.yaml through unsanitized YAML parameters could allow remote attackers to break out of an image, and execute e.g. malicious containers.

From the GitHub advisory

Impact A critical command injection vulnerability has been identified in the Rancher Manager cluster import endpoint /v3/import/{token}{clusterId}.yaml through unsanitized YAML parameters. This endpoint accepts an authImage query parameter that is rendered without sanitization into a generated Kubernetes manifest template. By including URL-encoded newlines in the parameter value, an attacker can break out of the image: field to inject arbitrary YAML keys and malicious configurations, such as commands to execute malicious containers.

Exploitation of this vulnerability requires the following conditions to be met: - Attackers must obtain a valid cluster registration token (these tokens may be exposed, for example, through documentation, screenshots, or insecure communication channels). - The victim’s cluster operator must execute kubectl apply against a maliciously crafted URL.

When a victim applies this compromised manifest using kubectl apply, a DaemonSet is deployed with the injected configuration. This DaemonSet: - Runs on all control-plane nodes with hostNetwork: true enabled. - Uses the cattle service account, which possesses cluster-admin privileges. - Mounts /etc/kubernetes directly from the host. - Executes attacker-controlled commands via the injected command: field.

An attacker who successfully exploits this vulnerability could:

- Achieve full control over downstream Kubernetes clusters. - Execute arbitrary code on control-plane nodes with elevated privileges. - Access sensitive cluster secrets and configurations via the privileged service account. - Disrupt cluster operations by manipulating critical control-plane workloads. - Establish persistent access through the deployed DaemonSet.

Weakness type: CWE-95.

Product: github.com/rancher/rancher (Go) · Assigned by: suse · Published: 2026-06-19

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: passive

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 1.31% probability of exploitation activity in the next 30 days; percentile 70.

Timeline

• 2026-06-19 — CVE record published by suse
• 2026-06-24 — CVE record last updated
• 2026-07-01 — GitHub-reviewed advisory GHSA-mhc6-2gfq-xx62 published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. github.com github.com

Vulnerability records

1. GitHub Advisory GHSA-mhc6-2gfq-xx62 github.com
2. CVE.org record CVE-2026-44939 cve.org
3. NVD entry CVE-2026-44939 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com

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