What is CVE-2026-56742?

CVE-2026-56742 is a medium-severity missing authorization vulnerability in github.com/cilium/cilium (go), affecting versions < 1.17.17. It is fixed in 1.17.17, 1.18.11, 1.19.5. The application does not perform an authorization check before performing a sensitive operation.

How severe is CVE-2026-56742?

CVE-2026-56742 has a CVSS score of 5.9 (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 packages are affected by CVE-2026-56742?

github.com/cilium/cilium (go) versions = 1.18.0, < 1.18.11.

Is there a fix for CVE-2026-56742?

Yes. CVE-2026-56742 is fixed in 1.17.17, 1.18.11, 1.19.5. Upgrade to this version or later.

Is CVE-2026-56742 exploitable, and should I be worried?

Whether CVE-2026-56742 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-2026-56742 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-2026-56742?

Upgrade: github.com/cilium/cilium to 1.17.17 or later, github.com/cilium/ciliumCilium to 1.18.11 or later, github.com/cilium/cilium to 1.19.5 or later.

CVE-2026-56742 in github.com/cilium/cilium

Q: How severe is CVE-2026-56742?

CVE-2026-56742 has a CVSS score of 5.9 (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.

Q: Which packages are affected by CVE-2026-56742?

github.com/cilium/cilium (go) versions = 1.18.0, < 1.18.11.

Q: Is there a fix for CVE-2026-56742?

Yes. CVE-2026-56742 is fixed in 1.17.17, 1.18.11, 1.19.5. Upgrade to this version or later.

Q: Is CVE-2026-56742 exploitable, and should I be worried?

Whether CVE-2026-56742 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-2026-56742 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-2026-56742?

Upgrade: github.com/cilium/cilium to 1.17.17 or later, github.com/cilium/ciliumCilium to 1.18.11 or later, github.com/cilium/cilium to 1.19.5 or later.

Summary

Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces

Workarounds

There is no workaround to this issue. Users of this feature who are unable to upgrade can mitigate the risk by ensuring that RBAC permissions to create HTTPRoute objects are only granted to cluster admins.

Acknowledgements

The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to @galanko for reporting the issue and @mhofstetter for their work on triaging and remediating this issue.

For more information

If you have any questions or comments about this advisory, please reach out on Slack.

If you think you have found a vulnerability affecting Cilium, we strongly encourage you to report it to our security mailing list at [email protected]. This is a private mailing list for the Cilium security team, and your report will be treated as top priority.

Impact

In Cilium clusters using Gateway API, users with permissions to create or update namespaced HTTPRoutes can mirror HTTP traffic to any Service in any namespace, bypassing the ReferenceGrant authorization mechanism.

Gateway API functionality is disabled by default.

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2026-56742 has a CVSS score of 5.9 (Medium). The vector is reachable from an adjacent network, 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 (1.17.17, 1.18.11, 1.19.5); upgrading removes the vulnerable code path.

Affected versions

github.com/cilium/cilium (< 1.17.17) github.com/cilium/ciliumCilium (>= 1.18.0, < 1.18.11) github.com/cilium/cilium (>= 1.19.0, < 1.19.5)

Security releases

github.com/cilium/cilium → 1.17.17 (go) github.com/cilium/ciliumCilium → 1.18.11 (go) github.com/cilium/cilium → 1.19.5 (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

This issue affects:

Cilium v1.19 from v1.19.0 to v1.19.4 inclusive
Cilium v1.18 from v1.18.0 to v1.18.10 inclusive
All versions of Cilium before v1.17.17

This issue is patched in:

Cilium v1.19.5
Cilium v1.18.11
Cilium v1.17.17

Frequently Asked Questions

What is CVE-2026-56742? CVE-2026-56742 is a medium-severity missing authorization vulnerability in github.com/cilium/cilium (go), affecting versions < 1.17.17. It is fixed in 1.17.17, 1.18.11, 1.19.5. The application does not perform an authorization check before performing a sensitive operation.
How severe is CVE-2026-56742? CVE-2026-56742 has a CVSS score of 5.9 (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 packages are affected by CVE-2026-56742?
- github.com/cilium/cilium (go) (versions < 1.17.17)
- github.com/cilium/ciliumCilium (go) (versions >= 1.18.0, < 1.18.11)
Is there a fix for CVE-2026-56742? Yes. CVE-2026-56742 is fixed in 1.17.17, 1.18.11, 1.19.5. Upgrade to this version or later.
Is CVE-2026-56742 exploitable, and should I be worried? Whether CVE-2026-56742 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-2026-56742 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-2026-56742?
- Upgrade github.com/cilium/cilium to 1.17.17 or later
- Upgrade github.com/cilium/ciliumCilium to 1.18.11 or later
- Upgrade github.com/cilium/cilium to 1.19.5 or later

Other vulnerabilities in github.com/cilium/cilium

CVE-IDSeverityPackage summary

CVE-2026-56743Mediumgithub.com/cilium/cilium: Cilium may unexpectedly allow ingress traffic from the local namespace when a Kubernetes NetworkPolicy is configured with an ipBlock match CVE-2026-53935Mediumgithub.com/cilium/cilium: CiliumLocalRedirectPolicy addressMatcher allows cross-namespace service traffic hijacking and can break service translation CVE-2026-49445Criticalgithub.com/cilium/cilium: Cilium vulnerable to sensitive information disclosure and cluster disruption via local Envoy admin socket access CVE-2026-41520Highgithub.com/cilium/cilium: Cillium exposes sensitive information included in the cilium-bugtool debug archive CVE-2026-33726Mediumgithub.com/cilium/cilium: Cilium L7 proxy may bypass Kubernetes NetworkPolicy for same-node traffic