CVE-2023-22651

Rancher Webhook is misconfigured during upgrade process

#!/bin/bash

set -euo pipefail

function prereqs() {
    if ! [ -x "$(command -v kubectl)" ]; then
      echo "error: kubectl is not installed." >&2
      exit 1
    fi

    if [[ -z "$(kubectl config view -o jsonpath='{.clusters[].cluster.server}')" ]]; then
        echo "error: No kubernetes cluster found on kubeconfig." >&2
        exit 1
    fi
}

function restart_deployment(){
    kubectl rollout restart deployment rancher-webhook -n cattle-system
    kubectl rollout status deployment rancher-webhook -n cattle-system --timeout=30s
}

function workaround() {
    echo "Cluster: $(kubectl config view -o jsonpath='{.clusters[].cluster.server}')"

    if ! kubectl get validatingwebhookconfigurations.admissionregistration.k8s.io rancher.cattle.io > /dev/null 2>&1; then
        echo "webhook rancher.cattle.io not found, restarting deployment:"
        restart_deployment

        echo "waiting for webhook configuration"
        sleep 15s
    fi

    local -i webhooks
    webhooks="$(kubectl get validatingwebhookconfigurations.admissionregistration.k8s.io rancher.cattle.io --no-headers | awk '{ print $2 }')"

    if [ "${webhooks}" == "0" ]; then
        echo "Webhook misconfiguration status: Cluster is affected by CVE-2023-22651"
        
        echo "Running workaround:"
        kubectl delete validatingwebhookconfiguration rancher.cattle.io
        restart_deployment

        ret=$?
        if [ $ret -eq 0 ]; then
            echo "Webhook restored, CVE-2023-22651 is fixed"
        else
            echo "error trying to restart deployment. try again in a few seconds."
        fi
    else
        echo "Webhook misconfiguration status: not present (skipping)"
    fi

    echo "Done"
}

function main() {
    prereqs
    workaround
}

main

A failure in the update logic of Rancher's admission Webhook may lead to the misconfiguration of the Webhook. This component enforces validation rules and security checks before resources are admitted into the Kubernetes cluster.

When the Webhook is operating in a degraded state, it no longer validates any resources, which may result in severe privilege escalations and data corruption.

The issue only affects users that upgrade from 2.6.x or 2.7.x to 2.7.2. Users that did a fresh install of 2.7.2 (and did not follow an upgrade path) are not affected.

The command below can be executed on the local cluster to determine whether the cluster is affected by this issue:

$ kubectl get validatingwebhookconfigurations.admissionregistration.k8s.io rancher.cattle.io

NAME                WEBHOOKS   AGE
rancher.cattle.io   0         19h

If the resulting webhook quantity is 0, the Rancher instance is affected.

The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access. Typical impact: privilege escalation beyond the intended level.

CVE-2023-22651 has a CVSS score of 9.9 (Critical). The vector is network-reachable, low 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 (2.7.3, 0.0.0-20230424183121-6d9a175954c6); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

Patched versions include release 2.7.3 and later versions.

1. What is CVE-2023-22651? CVE-2023-22651 is a critical-severity improper privilege management vulnerability in github.com/rancher/rancher (go), affecting versions = 2.7.2. It is fixed in 2.7.3, 0.0.0-20230424183121-6d9a175954c6. The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access.
2. How severe is CVE-2023-22651? CVE-2023-22651 has a CVSS score of 9.9 (Critical). 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/rancher/rancher are affected by CVE-2023-22651? github.com/rancher/rancher (go) versions = 2.7.2 is affected.
4. Is there a fix for CVE-2023-22651? Yes. CVE-2023-22651 is fixed in 2.7.3, 0.0.0-20230424183121-6d9a175954c6. Upgrade to this version or later.
5. Is CVE-2023-22651 exploitable, and should I be worried? Whether CVE-2023-22651 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-2023-22651 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-2023-22651?
   • Upgrade github.com/rancher/rancher to 2.7.3 or later
   • Upgrade github.com/rancher/rancher to 0.0.0-20230424183121-6d9a175954c6 or later

Other vulnerabilities in github.com/rancher/rancher