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MEDIUM severity

CVE-2021-36156 — loki

MEDIUMFix: grafana/loki#4020

CVE-2021-36156 is a medium-severity (CVSS 5.3) Path Traversal vulnerability in github.com/grafana/loki. A fix is available for github.com/grafana/loki — see the affected versions and patch details below.

Path traversal in Grafana Loki

Also known asGHSA-grj5-8x6q-hc9q
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs73th percentile — riskier than 73% of all scored CVEsHighest risk
0.00%0.66%1.33%1.99%0.3%1.5%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-36156 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐹github.com/grafana/loki

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

An issue was discovered in Grafana Loki through 2.2.1. The header value X-Scope-OrgID is used to construct file paths for rules files, and if crafted to conduct directory traversal such as ae ../../sensitive/path/in/deployment pathname, then Loki will attempt to parse a rules file at that location and include some of the contents in the error message.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/grafana/lokiall versions2.3.0go get github.com/grafana/loki@v2.3.0

Affected Products

1 product · 1 configurations
Application
lokigrafana
≤ 2.2.1
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/grafana/loki, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/grafana/loki to 2.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-36156 is resolved across your whole dependency graph.

  3. Workarounds

    Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

An issue was discovered in Grafana Loki through 2.2.1. The header value X-Scope-OrgID is used to construct file paths for rules files, and if crafted to conduct directory traversal such as ae ../../sensitive/path/in/deployment pathname, then Loki will attempt to parse a rules file at that location and include some of the contents in the error message.
O3 Security · Impact-Aware SCA

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CVE-2021-36156: loki Path Traversal — Fixed in 2.3.0