PatchTheCVECVE-2026-21726: The CVE-2021-36156 fix validates the namespace parameter for path traversal sequences after a single URL decod
CVE-2026-21726 is a medium-severity flaw (CVSS 5.3) affecting loki. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 this priority
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.4% (top 65%) |
| CISA exploited list | No |
| Weakness | CWE-22 |
| Published | 2026-04-15 |
| Last modified | 2026-10-26 |
Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-21726?
loki: upgrade to 3.6.4. Exact commands for each OS are on this page.
Is CVE-2026-21726 being exploited?
CVE-2026-21726 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-21726 affect?
CVE-2026-21726 affects loki. Severity is medium (CVSS 5.3). 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 Sun
How urgent is CVE-2026-21726?
Priority 32/100. Remotely exploitable, no login, no user action