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HIGH severity

CVE-2026-41520 — cilium

HIGH

CVE-2026-41520 is a high-severity (CVSS 7.9) Information Exposure vulnerability in github.com/cilium/cilium. A fix is available for github.com/cilium/cilium — see the affected versions and patch details below.

Cillium exposes sensitive information included in the cilium-bugtool debug archive

Also known asBIT-cilium-2026-41520BIT-cilium-operator-2026-41520BIT-hubble-relay-2026-41520GHSA-gj49-89wh-h4gjGO-2026-5400
Published
Updated
Affected
3 pkgs
Patched
3 / 3
Exploits
None indexed
Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • 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-2026-41520.

EPSS Exploitation Probability

via FIRST.org ↗
0.1%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs0th percentile — riskier than 0% of all scored CVEsHighest risk
0.00%0.19%0.39%0.58%0.0%0.1%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

3 pkgs affected
🐹github.com/cilium/cilium🐹github.com/cilium/cilium🐹github.com/cilium/cilium

Real-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

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.

Patches

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

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.

Affected Packages

3 total 3 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/cilium/ciliumall versions1.17.15go get github.com/cilium/cilium@v1.17.15
🐹Gogithub.com/cilium/cilium≥ 1.18.0&&< 1.18.91.18.9go get github.com/cilium/cilium@v1.18.9
🐹Gogithub.com/cilium/cilium≥ 1.19.0&&< 1.19.31.19.3go get github.com/cilium/cilium@v1.19.3

Affected Products

1 product · 3 configurations
Application
ciliumcilium
≥ 1.19.0 && < 1.19.3
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    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.

  2. Fix

    Update github.com/cilium/cilium to 1.17.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41520 is resolved across your whole dependency graph.

  3. Workarounds

    Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Frequently Asked Questions

### 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](https://docs.cilium.io/en/stable/security/network/encryption-wireguard/) 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
O3 Security · Impact-Aware SCA

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CVE-2026-41520: cilium — Fixed in 1.17.15