Summary
Workarounds
Disable IPv6 routing (IPv6 is disabled by default).
Acknowledgements
The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to Yusuke Suzuki for both highlighting and fixing the issue.
For more information
If you have any questions or comments about this advisory, please reach out on Slack.
As usual, if you think you found a related vulnerability, we strongly encourage you to report security vulnerabilities to our private security mailing list: [email protected] - first, before disclosing them in any public forums. This is a private mailing list where only members of the Cilium internal security team are subscribed to, and is treated as top priority.
Impact
Under specific conditions, Cilium may misattribute the source IP address of traffic to a cluster, identifying external traffic as coming from the host on which Cilium is running. As a consequence, network policies for that cluster might be bypassed, depending on the specific network policies enabled. Only IPv6 traffic is impacted by this vulnerability.
This issue only manifests when:
- Cilium is routing IPv6 traffic, and
- Kube-proxy is used for service handling, and
- NodePorts are used to route traffic to pods.
IPv6 is disabled by default. Cilium's kube-proxy replacement feature is not affected by this vulnerability.
The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.
CVE-2023-27594 has a CVSS score of 4.2 (Medium). The vector is reachable from an adjacent network, 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 (1.11.15, 1.12.8, 1.13.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
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.
Remediation advice
The problem has been fixed and is available on versions >=1.11.15, >=1.12.8, >=1.13.1
Frequently Asked Questions
- What is CVE-2023-27594? CVE-2023-27594 is a medium-severity incorrect authorization vulnerability in github.com/cilium/cilium (go), affecting versions < 1.11.15. It is fixed in 1.11.15, 1.12.8, 1.13.1. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
- How severe is CVE-2023-27594? CVE-2023-27594 has a CVSS score of 4.2 (Medium). 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/cilium/cilium are affected by CVE-2023-27594? github.com/cilium/cilium (go) versions < 1.11.15 is affected.
- Is there a fix for CVE-2023-27594? Yes. CVE-2023-27594 is fixed in 1.11.15, 1.12.8, 1.13.1. Upgrade to this version or later.
- Is CVE-2023-27594 exploitable, and should I be worried? Whether CVE-2023-27594 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-2023-27594 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-2023-27594?
- Upgrade
github.com/cilium/ciliumto 1.11.15 or later - Upgrade
github.com/cilium/ciliumto 1.12.8 or later - Upgrade
github.com/cilium/ciliumto 1.13.1 or later
- Upgrade