CVE-2026-41520: Cilium Bugtool Leaks Sensitive WireGuard Data
The National Vulnerability Database has issued an advisory for CVE-2026-41520, impacting Cilium, a critical eBPF-based networking and security solution. Prior to versions 1.17.15, 1.18.9, and 1.19.3, the cilium-bugtool utility could inadvertently expose sensitive data. This leakage occurs specifically when the tool is executed against Cilium deployments where WireGuard encryption is enabled.
This is a high-severity issue, with a CVSS score of 7.9, categorized under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) and CWE-312 (Cleartext Storage of Sensitive Information). The vulnerability essentially turns a diagnostic tool into a data exfiltration vector, making it a serious concern for organizations relying on Cilium for secure, observable Kubernetes networking. An attacker with high privileges, able to run cilium-bugtool, could gain access to configuration or cryptographic material that should remain confidential.
For defenders, the immediate priority is patching. The National Vulnerability Database confirms that this issue has been resolved in Cilium versions 1.17.15, 1.18.9, and 1.19.3. Organizations must upgrade their Cilium deployments to these patched versions to mitigate the risk of sensitive data exposure. Failure to do so leaves a backdoor for privileged attackers to harvest critical information from WireGuard-encrypted clusters.
What This Means For You
- If your organization uses Cilium with WireGuard encryption, you are exposed. Immediately verify your Cilium version. If it's older than 1.17.15, 1.18.9, or 1.19.3, you need to upgrade. Patching is not optional here; it's a critical step to prevent sensitive data leakage from your eBPF-based network.
Related ATT&CK Techniques
🛡️ Detection Rules
3 rules · 6 SIEM formats3 detection rules auto-generated for this incident, mapped to MITRE ATT&CK. Sigma YAML is free — export to any SIEM format via the Intel Bot.
CVE-2026-41520: Cilium Bugtool Sensitive Data Leak
title: CVE-2026-41520: Cilium Bugtool Sensitive Data Leak
id: scw-2026-05-08-ai-1
status: experimental
level: high
description: |
Detects the execution of the 'cilium-bugtool' binary. This tool, when run on vulnerable versions of Cilium with WireGuard enabled, can leak sensitive WireGuard encryption data. This rule is the primary indicator for the initial exploitation of CVE-2026-41520.
author: SCW Feed Engine (AI-generated)
date: 2026-05-08
references:
- https://shimiscyberworld.com/posts/nvd-CVE-2026-41520/
tags:
- attack.discovery
- attack.t1074
logsource:
category: process_creation
detection:
selection:
Image|endswith:
- '/cilium-bugtool'
condition: selection
falsepositives:
- Legitimate administrative activity
Source: Shimi's Cyber World · License & reuse
Indicators of Compromise
| ID | Type | Indicator |
|---|---|---|
| CVE-2026-41520 | Information Disclosure | Cilium < 1.17.15 |
| CVE-2026-41520 | Information Disclosure | Cilium < 1.18.9 |
| CVE-2026-41520 | Information Disclosure | Cilium < 1.19.3 |
| CVE-2026-41520 | Information Disclosure | cilium-bugtool output when WireGuard encryption is enabled |
Written by SCW Vulnerability Desk
Source & Attribution
| Source Platform | NVD |
| Channel | National Vulnerability Database |
| Published | May 09, 2026 at 02:16 UTC |
This content was AI-rewritten and enriched by Shimi's Cyber World based on the original source. All intellectual property rights remain with the original author.
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