Summary
Workarounds
There is no workaround to this issue.
Users who have previously shared bugtool or sysdump archives from WireGuard-enabled nodes should rotate the WireGuard keys on the affected nodes. This can be done by deleting the key file and restarting the Cilium agent, which will generate a new key pair.
Acknowledgements
The Cilium community has worked together with members of Isovalent to prepare these mitigations. Cillium extends special thanks to @kodareef5 for reporting the issue and @tklauser for their work on triaging and remediating this issue.
For more information
If there are any questions or comments about this advisory, please reach out on Slack.
Cilium strongly encourages the reporting of suspected vulnerabilities to the security mailing list at [email protected]. This is a private mailing list for the Cilium security team, and the report will be treated as top priority.
Impact
The output of cilium-bugtool can contain sensitive data when the tool is run against Cilium deployments with WireGuard encryption enabled.
Users of WireGuard Transparent Encryption are affected.
The sensitive data is the WireGuard private key (cilium_wg0.key) used for node-to-node encrypted communication
cilium-bugtool is a debugging tool that is typically invoked manually and does not run during the normal operation of a Cilium cluster. It is also invoked when gathering sysdumps using the Cilium CLI's cilium sysdump command.
CVE-2026-41520 has a CVSS score of 7.9 (High). The vector is requires local access, 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 (1.17.15, 1.18.9, 1.19.3); 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
This issue affects:
- Cilium v1.19 between v1.19.0 and v1.19.2 inclusive
- Cilium v1.18 between v1.18.0 and v1.18.8 inclusive
- All versions of Cilium prior to v1.17.15
This issue has been patched in:
- Cilium v1.19.3
- Cilium v1.18.9
- Cilium v1.17.15
Frequently Asked Questions
- What is CVE-2026-41520? CVE-2026-41520 is a high-severity security vulnerability in github.com/cilium/cilium (go), affecting versions < 1.17.15. It is fixed in 1.17.15, 1.18.9, 1.19.3.
- How severe is CVE-2026-41520? CVE-2026-41520 has a CVSS score of 7.9 (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/cilium/cilium are affected by CVE-2026-41520? github.com/cilium/cilium (go) versions < 1.17.15 is affected.
- Is there a fix for CVE-2026-41520? Yes. CVE-2026-41520 is fixed in 1.17.15, 1.18.9, 1.19.3. Upgrade to this version or later.
- Is CVE-2026-41520 exploitable, and should I be worried? Whether CVE-2026-41520 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-2026-41520 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-2026-41520?
- Upgrade
github.com/cilium/ciliumto 1.17.15 or later - Upgrade
github.com/cilium/ciliumto 1.18.9 or later - Upgrade
github.com/cilium/ciliumto 1.19.3 or later
- Upgrade