CVE-2026-21726

Executive Summary

The Loki Path Traversal - CVE-2021-36156 Bypass vulnerability is a medium-severity issue that can be exploited to read files at the Ruler API endpoint. The likelihood of exploitation is relatively low, but the potential business impact is moderate due to the risk of unauthorized access to sensitive information. The vulnerability can be exploited remotely without any privileges or authentication.

The affected systems and components are not explicitly listed, but the vulnerability is specific to the Loki API endpoint /loki/api/v1/rules/{namespace}. The vulnerability is currently open, and no patch or fix has been released yet. The CISA KEV status is 'No', indicating that this vulnerability is not currently being tracked by the CISA Known Exploited Vulnerabilities catalog. The vulnerability was published on 2026-04-15T00:00:00.000000Z, and thanks to Prasanth Sundararajan for reporting this issue.

Exploitation Context

A realistic exploitation scenario involves an attacker sending specially crafted requests to the affected endpoint to read sensitive files, which can be used for reconnaissance or to gain valuable insights into the target system. The attacker's motivation to exploit this vulnerability is likely driven by the desire to access sensitive information, which can be used for malicious purposes such as identity theft, financial fraud, or other types of cybercrime.

Patch Priority

Recommended Actions

• Apply the official patch or fix as soon as it becomes available
• Implement additional security measures, such as input validation and sanitization, to prevent path traversal attacks
• Monitor the affected endpoint for suspicious activity and potential exploitation attempts
• Update the vulnerability management process to include regular checks for similar issues

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