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Loki EUVDEUVD-2026-23100

| CVE-2026-21726 MEDIUM
Path Traversal (CWE-22)
2026-04-15 security@grafana.com
Path Traversal Grafana Loki
5.3
CVSS 3.1 · Vendor: grafana
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Vulnerability Assessment

Weakness
CWE
CWE-22
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V5 - File Handling Path canonicalization, traversal prevention
MITRE ATT&CK

2 techniques across 2 tactics: Discovery, Collection

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Jul 26, 2026

Path traversal in Grafana Loki 2.3.0 through 3.5.8 allows unauthenticated remote attackers to read arbitrary files on the server via double encoding of the namespace parameter in the Ruler API endpoint /loki/api/v1/rules/{namespace}. This bypasses the fix for CVE-2021-36156, which sanitized the parameter only after a single URL decode. While the CVSS base score is 5.3 (Medium), EPSS exploitation probability is extremely low (0.01%), and no active exploitation or public exploit code is known.

Affected VersionsENISA

Loki 2.3.0 <3.5.9

Affected Packages

go github.com/grafana/loki no fix
go github.com/grafana/loki/v3 fix: 3.6.4
euvd loki fix: 3.5.9

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 3 packages in go, euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Vendor (grafana) PRIMARY 5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
SUSE MEDIUM
Red Hat 5.3 MEDIUM

Primary rating from Vendor (grafana).

CVSS VectorVendor: grafana

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

Lifecycle Timeline

3
Patch released
Apr 20, 2026 - 20:08 nvd
Patch available
Patch available
Apr 16, 2026 - 05:29 EUVD
3.5.9
CVE Published
Apr 15, 2026 - 20:16 nvd
MEDIUM 5.3

DescriptionCVE.org

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.

Threat Intelligence Overview

EPSS Score
0.0%
Top 99% exploitable
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

26
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +26
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Path Traversal HIGH

Path traversal exploits occur when applications use user-controlled input to construct file system paths without proper validation.

More in Loki

View all
CVE-2026-21729 HIGH
7.5 Jul 16

Uncontrolled memory allocation in Grafana Loki lets remote unauthenticated users issue queries with excessively large li
CVE-2021-36156 MEDIUM
5.3 Aug 03

An issue was discovered in Grafana Loki through 2.2.1. Rated medium severity (CVSS 5.3), this vulnerability is remotely

Same weakness CWE-22 – Path Traversal

View all
CVE-2019-3396 CRITICAL POC
9.8
CVE-2019-19781 CRITICAL POC
9.8
CVE-2020-5902 CRITICAL POC
9.8
CVE-2021-21972 CRITICAL POC
9.8
CVE-2021-40444 HIGH POC
8.8
CVE-2022-41352 CRITICAL POC
9.8
CVE-2021-27065 HIGH POC
7.8
CVE-2019-11510 CRITICAL POC
10.0

Same technique Path Traversal

View all
CVE-2018-20250 HIGH POC
7.8
CVE-2022-37042 CRITICAL POC
9.8
CVE-2025-64446 CRITICAL POC
9.8

Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Module for Package Hub 15 SP7 Fixed
SUSE Manager Client Tools 15 Fixed
SUSE Manager Client Tools for SLE 15 Fixed
SUSE Multi-Linux Manager Client Tools for SLE 15 Fixed
openSUSE Leap 15.6 Fixed

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-21726 ADVISORY https://vuldb.com/vuln/357839 REF https://grafana.com/security/security-advisories/cve-2026-21726

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