CVE-2023-27594 — cilium
MEDIUMCVE-2023-27594 is a medium-severity (CVSS 4.2) CWE-285 vulnerability in github.com/cilium/cilium. A fix is available for github.com/cilium/cilium — see the affected versions and patch details below.
Cilium vulnerable to potential network policy bypass when routing IPv6 traffic
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-27594.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-27594 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/cilium/cilium🐹github.com/cilium/cilium🐹github.com/cilium/ciliumReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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.
Patches
The problem has been fixed and is available on versions >=1.11.15, >=1.12.8, >=1.13.1
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/cilium/cilium | all versions | 1.11.15go get github.com/cilium/cilium@v1.11.15 |
| 🐹Go | github.com/cilium/cilium | ≥ 1.12.0&&< 1.12.8 | 1.12.8go get github.com/cilium/cilium@v1.12.8 |
| 🐹Go | github.com/cilium/cilium | ≥ 1.13.0&&< 1.13.1 | 1.13.1go get github.com/cilium/cilium@v1.13.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cilium/cilium, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/cilium/cilium to 1.11.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-27594 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-27594 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-27594. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-27594 in your dependencies?
O3 Security finds CVE-2023-27594 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.