CVE-2021-36156: Github.com/grafana/loki Path Traversal Vulnerability

MODERATE
Advisory Identifier: GHSA-grj5-8x6q-hc9q
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CVSS 5.3
CWE-22
Published
Advisory Summary

CVE-2021-36156 is a MODERATE (CVSS 5.3) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Github.com/grafana/loki libraries in the Go ecosystem. The issue involves path traversal in grafana loki. Remediation is available by upgrading affected packages to version 2.3.0.

CVE-2021-36156 at a Glance

CVE Identifier CVE-2021-36156
GHSA Identifier GHSA-grj5-8x6q-hc9q
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Github.com/grafana/loki
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2021-36156

To remediate this vulnerability, upgrade all affected Github.com/grafana/loki dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/grafana/loki fixed: 2.3.0 
Upgrade github.com/grafana/loki to 2.3.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/grafana/loki

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-36156, inspect your project dependencies for Github.com/grafana/loki:

inspect dependencies for github.com/grafana/loki

Analyze the terminal output to locate any version of Github.com/grafana/loki in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.3.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Github.com/grafana/loki, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2021-36156 Affected Github.com/grafana/loki Versions

1 component(s)
Fixed Versions:
2.3.0
Product / Package Ecosystem Affected Versions Fixed Version
github.com/grafana/loki
golang/github.com/grafana/loki
Go
< 2.3.0
2.3.0

References

NVD — CVE-2021-36156 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-36156
Github.com/grafana/loki Source Repository REPOSITORY
https://github.com/grafana/loki/pull/4020
Github.com/grafana/loki Source Repository REPOSITORY
https://github.com/grafana/loki/pull/4020#issue-694377133
Github.com/grafana/loki Source Repository REPOSITORY
https://github.com/grafana/loki
Github.com/grafana/loki Release RELEASE
https://github.com/grafana/loki/releases/tag/v2.3.0

Frequently Asked Questions

What is CVE-2021-36156?
CVE-2021-36156 is a security vulnerability in Github.com/grafana/loki involving Path traversal in Grafana Loki under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Github.com/grafana/loki versions are affected?
Affected versions include releases prior to 2.3.0 across affected packages: github.com/grafana/loki.
What version fixes CVE-2021-36156?
Upgrading to 2.3.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/grafana/loki affected?
Yes, github.com/grafana/loki is affected in releases prior to 2.3.0. Upgrade your dependency to 2.3.0 or later.
What is the CVSS score of CVE-2021-36156?
CVE-2021-36156 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2021-36156?
CVE-2021-36156 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check Go dependencies for CVE-2021-36156?
Run the dependency tree command: 'inspect dependencies for github.com/grafana/loki'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-grj5-8x6q-hc9q",
  "modified" : "2021-09-08T18:11:29Z",
  "published" : "2021-09-02T22:00:40Z",
  "aliases" : [ "CVE-2021-36156" ],
  "summary" : "Path traversal in Grafana Loki",
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/grafana/loki"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.3.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-36156"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/grafana/loki/pull/4020"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/grafana/loki/pull/4020#issue-694377133"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/grafana/loki"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/grafana/loki/releases/tag/v2.3.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-04T18:52:20Z",
    "nvd_published_at" : "2021-08-03T15:15:00Z"
  }
}