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.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Scope Changed

Confidentiality Impact High

Integrity Impact None

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Exploitation none

Automatable no

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Grafana Enterprise Metrics (GEM) unaffected
Version Status Constraints
2.11.0 affected ≤ 2.16.2
2.17.0 affected < 2.17.20
Grafana Grafana Mimir unaffected
Version Status Constraints
3.0.4 affected < 3.1.7
3.2.0 affected < 3.2.2

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Project Subscriptions

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Advisories

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Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://grafana.com/security/security-advisories/cve-2026-81938 cve-icon cve-icon
History

Mon, 02 Nov 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Mon, 02 Nov 2026 18:30:00 +0000

Type Values Removed Values Added
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.
Title Arbitrary file read via Alertmanager receiver configuration in Grafana Mimir
Weaknesses CWE-22
References
Metrics cvssV3_1

{'score': 7.7, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GRAFANA

Published:

Updated: 2026-11-02T19:06:58.641Z

Reserved: 2026-08-27T19:29:04.581Z

Link: CVE-2026-81938

cve-icon Vulnrichment

Updated: 2026-11-02T19:06:51.426Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-11-02T19:18:11.127

Modified: 2026-11-02T19:34:23.993

Link: CVE-2026-81938

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-11-02T20:00:04Z

Weaknesses