CVE-2026-81938
Arbitrary file read via Alertmanager receiver configuration in Grafana Mimir
Grafana Mimir's Alertmanager rejects tenant-supplied receiver configurations that reference local files, but the check did not cover two HTTP client settings: http_headers.<name>.files and basic_auth.username_file. A tenant permitted to upload an Alertmanager configuration could point these fields at any file readable by the Alertmanager process. When a notification was sent, Alertmanager read the file and put its contents in a header of the outgoing request. By directing the receiver at a server they control, the tenant could read files from the Alertmanager host, such as credentials and configuration. Exploitation requires permission to write the tenant's Alertmanager configuration. Grafana Enterprise Metrics (GEM), which is built on Mimir, is also affected. The issue is fixed in Mimir 3.1.7 and 3.2.2 and in GEM 2.17.20. GEM 2.11 through 2.16 will not receive a fix; users on those versions should upgrade to 2.17.20 or later.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| Enterprise Metrics (GEM) Grafana |
≥ 2.11.0; ≤ 2.16.2 (affected, semver) ≥ 2.17.0; < 2.17.20 (affected, semver) Other versions: unaffected |
CNA: GRAFANA |
| Grafana Mimir Grafana |
≥ 3.0.4; < 3.1.7 (affected, semver) ≥ 3.2.0; < 3.2.2 (affected, semver) Other versions: unaffected |
CNA: GRAFANA |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 7.7 high |
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N | CNA: GRAFANA |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://grafana.com/security/security-advisories/cve-2026-81938CNA: GRAFANA · vendor-advisory
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