# CVE-2026-81938: Arbitrary file read via Alertmanager receiver configuration in Grafana Mimir

> CVE-2026-81938: Arbitrary file read via Alertmanager receiver configuration in Grafana Mimir. CVSS 7.7 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-81938
Last updated: 2026-11-02T19:34:23Z

- Published: 2026-11-02 18:23 UTC · Updated: 2026-11-02 19:34 UTC · Assigner: GRAFANA
- CVSS: 7.7 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
- EPSS: 0.39%, 34th percentile (scored 2026-11-04)
- CISA KEV: no
- CWE: CWE-22

## Description

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.

## Affected vendors and products

- Grafana: Enterprise Metrics (GEM)
- Grafana: Grafana Mimir

## Tracked companies

- [Grafana Cloud](https://rewindex.com/company/grafana-cloud.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-81938)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-81938)
- [https://grafana.com/security/security-advisories/cve-2026-81938](https://grafana.com/security/security-advisories/cve-2026-81938)

---

_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


---
Canonical: https://rewindex.com/cve/CVE-2026-81938 · Markdown: https://rewindex.com/cve/CVE-2026-81938.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-81938 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-11-05T14:47:36.764Z