Loki Path Traversal - CVE-2021-36156 Bypass
Priority LOW 24CWE-22Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Information disclosure, Spoofing
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- Partial Red Hat: 8 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-22, CWE-601 and the CVSS impact.
Summary
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00409 35th percentileScored 2026-11-07
Fix Partial Loki (Grafana): 3.5.9github.com/grafana/loki/v3 (Go): 3.6.4Red Hat: 8 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Grafana | Loki | 2.3.0 to before 3.5.9 | 3.5.9 | Patch available | CNA |
| — | github.com/grafana/loki/v3 (Go) | before 3.6.4 | 3.6.4 | Patch available | GHSA-497x-rrr9-68jp |
- Loki VendorGrafana Affected 2.3.0 to before 3.5.9 Fixed in 3.5.9 Patch available CNA
- github.com/grafana/loki/v3 (Go) Vendor— Affected before 3.6.4 Fixed in 3.6.4 Patch available GHSA-497x-rrr9-68jp
Remediation
- Fix · CNA Loki (Grafana) Fixed in 3.5.9
- Fix · GHSA-497x-rrr9-68jp github.com/grafana/loki/v3 (Go) Fixed in 3.6.4 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Logging Subsystem for Red Hat OpenShift | Affected | No fix yet: Fix deferred |
| Multicluster Global Hub | Affected | No fix yet: Fix deferred |
| Network Observability Operator | Affected | No fix yet: Fix deferred |
| Red Hat Advanced Cluster Management for Kubernetes 2 | Affected | No fix yet: Fix deferred |
| Red Hat Ceph Storage 6 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat OpenStack Platform 18.0 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-21726
- 2026-10-03 Alias added: GHSA-497x-rrr9-68jp
References
More Grafana Loki vulnerabilities
- TI-2021-14575 An issue was discovered in Grafana Loki through 2.2.1. CVSS 3.1MEDIUM 5.3
Sources
- CVE-2026-21726 · CVE Program
- CVE-2026-21726 · NVD
- FIRST EPSS
- GHSA-497x-rrr9-68jp · GitHub Advisory Database · CC BY 4.0
- CVE-2026-21726 · Red Hat security data · CC BY 4.0
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