CVE-2021-36156

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.

Published: 2021-08-03 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-36156 is rated Moderate Risk (46/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.49%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-36156

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-25 1.45% 1.49% +0.04%
2 2026-06-15 0.25% 1.45% +1.19%
3 2026-03-31 — 0.25% —

Full EPSS history (13 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-36156

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-36156

GitHub Security Advisory for CVE-2021-36156

OS Trackers for CVE-2021-36156

vendor priority summary link
redhat medium — https://access.redhat.com/security/cve/CVE-2021-36156

Affected software / configurations for CVE-2021-36156

Vendor Product Version Raw CPE
grafana loki <= 2.2.1 cpe:2.3:a:grafana:loki:*:*:*:*:*:*:*:*

References for CVE-2021-36156

URL Tags
https://github.com/grafana/loki/pull/4020#issue-694377133 Issue Tracking Third Party Advisory
https://github.com/grafana/loki/releases/tag/v2.3.0 Patch Third Party Advisory
cvelogic Threat Intelligence