CVE-2026-21726: Vulnerability in Grafana Loki
The CVE-2021-36156 fix validates the namespace parameter for path traversal sequences after a single URL decode, by double encoding, an attacker can read files at the Ruler API endpoint /loki/api/v1/rules/{namespace} Thanks to Prasanth Sundararajan for reporting this vulnerability.
AI Analysis
Technical Summary
This vulnerability in Grafana Loki 2.3.0 involves improper validation of the namespace parameter in the Ruler API endpoint. Although a previous fix (CVE-2021-36156) validated the parameter after a single URL decode, an attacker can bypass this by double encoding the path traversal sequences, allowing unauthorized file reads. The vulnerability is classified under CWE-22 (Path Traversal). No official remediation or patch is currently documented.
Potential Impact
An attacker without privileges can read arbitrary files on the server hosting Grafana Loki by exploiting the path traversal vulnerability in the Ruler API endpoint. This could lead to disclosure of sensitive information. There is no indication of impact on integrity or availability, and no known active exploitation has been reported.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, restrict access to the Ruler API endpoint and monitor for suspicious requests involving encoded path traversal sequences. Avoid exposing the Loki Ruler API to untrusted networks.
CVE-2026-21726: Vulnerability in Grafana Loki
Description
The CVE-2021-36156 fix validates the namespace parameter for path traversal sequences after a single URL decode, by double encoding, an attacker can read files at the Ruler API endpoint /loki/api/v1/rules/{namespace} Thanks to Prasanth Sundararajan for reporting this vulnerability.
CVSS v3.1
Score 5.3medium
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability in Grafana Loki 2.3.0 involves improper validation of the namespace parameter in the Ruler API endpoint. Although a previous fix (CVE-2021-36156) validated the parameter after a single URL decode, an attacker can bypass this by double encoding the path traversal sequences, allowing unauthorized file reads. The vulnerability is classified under CWE-22 (Path Traversal). No official remediation or patch is currently documented.
Potential Impact
An attacker without privileges can read arbitrary files on the server hosting Grafana Loki by exploiting the path traversal vulnerability in the Ruler API endpoint. This could lead to disclosure of sensitive information. There is no indication of impact on integrity or availability, and no known active exploitation has been reported.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, restrict access to the Ruler API endpoint and monitor for suspicious requests involving encoded path traversal sequences. Avoid exposing the Loki Ruler API to untrusted networks.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GRAFANA
- Date Reserved
- 2026-01-05T09:26:06.215Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69dfeeb382d89c981f942271
Added to database: 4/15/2026, 8:01:55 PM
Last enriched: 5/14/2026, 2:15:16 AM
Last updated: 5/31/2026, 2:36:39 AM
Views: 123
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