What is CVE-2023-32186?

CVE-2023-32186 is a high-severity allocation of resources without limits or throttling vulnerability in github.com/rancher/rke2 (go), affecting versions < 1.24.17. It is fixed in 1.24.17, 1.25.13, 1.26.8, 1.27.5, 1.28.1. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.

How severe is CVE-2023-32186?

CVE-2023-32186 has a CVSS score of 7.5 (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.

Which versions of github.com/rancher/rke2 are affected by CVE-2023-32186?

github.com/rancher/rke2 (go) versions < 1.24.17 is affected.

Is there a fix for CVE-2023-32186?

Yes. CVE-2023-32186 is fixed in 1.24.17, 1.25.13, 1.26.8, 1.27.5, 1.28.1. Upgrade to this version or later.

Is CVE-2023-32186 exploitable, and should I be worried?

Whether CVE-2023-32186 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.

What actually determines whether CVE-2023-32186 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.

How do I fix CVE-2023-32186?

Upgrade: github.com/rancher/rke2 to 1.24.17 or later, github.com/rancher/rke2 to 1.25.13 or later, github.com/rancher/rke2 to 1.26.8 or later, github.com/rancher/rke2 to 1.27.5 or later, github.com/rancher/rke2 to 1.28.1 or later.

CVE-2023-32186 in github.com/rancher/rke2

Q: How severe is CVE-2023-32186?

CVE-2023-32186 has a CVSS score of 7.5 (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.

Q: Which versions of github.com/rancher/rke2 are affected by CVE-2023-32186?

github.com/rancher/rke2 (go) versions < 1.24.17 is affected.

Q: Is there a fix for CVE-2023-32186?

Yes. CVE-2023-32186 is fixed in 1.24.17, 1.25.13, 1.26.8, 1.27.5, 1.28.1. Upgrade to this version or later.

Q: Is CVE-2023-32186 exploitable, and should I be worried?

Whether CVE-2023-32186 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.

Q: What actually determines whether CVE-2023-32186 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.

Q: How do I fix CVE-2023-32186?

Upgrade: github.com/rancher/rke2 to 1.24.17 or later, github.com/rancher/rke2 to 1.25.13 or later, github.com/rancher/rke2 to 1.26.8 or later, github.com/rancher/rke2 to 1.27.5 or later, github.com/rancher/rke2 to 1.28.1 or later.

Summary

RKE2 supervisor port is vulnerable to unauthenticated remote denial-of-service (DoS) attack via TLS SAN stuffing attack

Mitigation

If you cannot upgrade to a fixed release, the certificate can be "frozen" by running the following command against the cluster:

kubectl annotate secret -n kube-system rke2-serving listener.cattle.io/static=true

⚠️ IMPORTANT CAUTION: Note that this mitigation will prevent the certificate from adding new SAN entries when servers join the cluster, and automatically renewing itself when it is about to expire. If you do this, you should delete the annotation when adding new servers to the cluster, or when the certificate is within 90 days of expiring, so that it can be updated. Once that is done, you can freeze it again.

Affected certificates can be reset by performing the following steps:

Run kubectl delete secret -n kube-system rke2-serving
Delete /var/lib/rancher/rke2/server/tls/dynamic-cert.json from all servers, and restart the rke2-server service.

Background

The RKE2 supervisor listens on port TCP 9345 and uses the rancher/dynamiclistener library to dynamically generate TLS certificates that contain TLS Subject Alternative Names (SAN) for any host name or IP address requested by a client. This is done to allow servers and external load-balancers to be added to the cluster without the administrator having to explicitly know and configure in advance a fixed list of endpoints that the supervisor may be hosted at.

The library allows the embedding application to configure a callback that is used to filter addresses requested by clients; but this was not previously implemented in RKE2.

For more information

If you have any questions or comments about this advisory:

Reach out to the SUSE Rancher Security team for security related inquiries.
Open an issue in the RKE2 repository.
Verify with our support matrix and product support lifecycle.

Impact

An issue was found in RKE2 where an attacker with network access to RKE2 servers' supervisor port (TCP 9345) can force the TLS server to add entries to the certificate's Subject Alternative Name (SAN) list, through a stuffing attack, until the certificate grows so large that it exceeds the maximum size allowed by TLS client implementations. OpenSSL for example will raise an excessive message size error when this occurs. No authentication is necessary to perform this attack, only the ability to perform a TLS handshake against the supervisor port (TCP 9345).

Affected servers will continue to operate, but clients (server or agent nodes) will fail to establish new connections when joining or rejoining the cluster, thus leading to a denial of service (DoS) attack.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2023-32186 has a CVSS score of 7.5 (High). The vector is network-reachable, no 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 (1.24.17, 1.25.13, 1.26.8, 1.27.5, 1.28.1); upgrading removes the vulnerable code path.

Affected versions

github.com/rancher/rke2 (< 1.24.17) github.com/rancher/rke2 (>= 1.25.0, < 1.25.13) github.com/rancher/rke2 (>= 1.26.0, < 1.26.8) github.com/rancher/rke2 (>= 1.27.0, < 1.27.5) github.com/rancher/rke2 (>= 1.28.0, < 1.28.1)

Security releases

github.com/rancher/rke2 → 1.24.17 (go) github.com/rancher/rke2 → 1.25.13 (go) github.com/rancher/rke2 → 1.26.8 (go) github.com/rancher/rke2 → 1.27.5 (go) github.com/rancher/rke2 → 1.28.1 (go)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade to a fixed release:

v1.28.1+rke2r1
v1.27.5+rke2r1
v1.26.8+rke2r1
v1.25.13+rke2r1
1.24.17+rke2r1

If you are using RKE2 1.27 or earlier, you must also add the parameter tls-san-security: true to the RKE2 configuration to enable enhanced security for the supervisor's TLS SAN list. This option defaults to true starting with RKE2 1.28.

Note that this flag changes the behavior of RKE2's supervisor listener. You should ensure that you configure node-external-ip on servers that will be connected to via an external IP, and add tls-san entries for any load-balancers or VIP addresses that will be associated with the supervisor port. External IPs and load-balancer/VIP addresses will no longer be added to the supervisor certificate's SAN list unless explicitly configured.

Frequently Asked Questions

What is CVE-2023-32186? CVE-2023-32186 is a high-severity allocation of resources without limits or throttling vulnerability in github.com/rancher/rke2 (go), affecting versions < 1.24.17. It is fixed in 1.24.17, 1.25.13, 1.26.8, 1.27.5, 1.28.1. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
How severe is CVE-2023-32186? CVE-2023-32186 has a CVSS score of 7.5 (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.
Which versions of github.com/rancher/rke2 are affected by CVE-2023-32186? github.com/rancher/rke2 (go) versions < 1.24.17 is affected.
Is there a fix for CVE-2023-32186? Yes. CVE-2023-32186 is fixed in 1.24.17, 1.25.13, 1.26.8, 1.27.5, 1.28.1. Upgrade to this version or later.
Is CVE-2023-32186 exploitable, and should I be worried? Whether CVE-2023-32186 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
What actually determines whether CVE-2023-32186 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.
How do I fix CVE-2023-32186?
- Upgrade github.com/rancher/rke2 to 1.24.17 or later
- Upgrade github.com/rancher/rke2 to 1.25.13 or later
- Upgrade github.com/rancher/rke2 to 1.26.8 or later
- Upgrade github.com/rancher/rke2 to 1.27.5 or later
- Upgrade github.com/rancher/rke2 to 1.28.1 or later

Other vulnerabilities in github.com/rancher/rke2

CVE-IDSeverityPackage summary

GHSA-X7XJ-JVWP-97RVCriticalgithub.com/rancher/rke2: RKE2 allows privilege escalation in Windows nodes due to Insecure Access Control Lists