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CVE-2026-81938

Arbitrary file read via Alertmanager receiver configuration in Grafana Mimir

High7.7
Published
Updated
Reserved
Assigned by
GRAFANA

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.

Scores

CVSS scores of CVE-2026-81938, by who scored it
Scored byCVSSScoreVector
GRAFANACNA (assigner)3.1High7.7CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
NVDNVD · Awaiting Analysis3.1High7.7CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
EPSS (exploitation in 30 days)
Not scored
CISA SSVC
Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.7.

Weakness

Affected products

  • Grafana · Enterprise Metrics (GEM)

    • affected 2.11.0 – ≤ 2.16.2
    • affected 2.17.0 – < 2.17.20

  • Grafana · Grafana Mimir

    • affected 3.0.4 – < 3.1.7
    • affected 3.2.0 – < 3.2.2

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

Record last updated .