Arbitrary file read via Alertmanager receiver configuration in Grafana Mimir

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-81938
StatePUBLISHED
AssignerGRAFANA
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-02 19:18:11 UTC
Updated2026-11-02 19:34:23 UTC
DescriptionGrafana 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.

Risk And Classification

Primary CVSS: v3.1 7.7 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Problem Types: CWE-22 | CWE-22 CWE-22

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.7HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
3.1CNADECLARED7.7HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Grafana Enterprise Metrics GEM affected 2.11.0 2.16.2 semver Not specified
CNA Grafana Enterprise Metrics GEM affected 2.17.0 2.17.20 semver Not specified
CNA Grafana Grafana Mimir affected 3.0.4 3.1.7 semver Not specified
CNA Grafana Grafana Mimir affected 3.2.0 3.2.2 semver Not specified

References

ReferenceSourceLinkTags
grafana.com/security/security-advisories/cve-2026-81938 [email protected] grafana.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: arang (en)

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