CVE-2026-21729Network attack vector

Unauthenticated service crash via unchecked query limit

Published Jul 16, 2026 · Updated Jul 16, 2026

Denial of service in Grafana Labs Grafana Loki 3.0.0 and later before 3.7.0 allows remote attackers to crash the service. The detected_fields endpoint allocates slices and maps with twice the user-supplied limit rather than the actual result count, so an empty-result query with an extreme limit can consume tens of GiB and exhaust memory. No authentication or matching log data is required; the resulting out-of-memory condition terminates an exposed Loki process and interrupts log-query availability.

CVSS severity7.5
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Grafana Labs Grafana Loki 3.0.0 and later before 3.7.0 allows remote attackers to crash the service. The detected_fields endpoint allocates slices and maps with twice the user-supplied limit rather than the actual result count, so an empty-result query with an extreme limit can consume tens of GiB and exhaust memory. No authentication or matching log data is required; the resulting out-of-memory condition terminates an exposed Loki process and interrupts log-query availability.

The record

CVE
CVE-2026-21729
Published
Jul 16, 2026
Updated
Jul 16, 2026
Vendor
Grafana Labs
Product
Grafana Loki
Classifications
CWE-770, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=v3.0.0 <v3.7.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Grafana Labs · Grafana Lokiversion=v3.0.0 <v3.7.0

Published CVSS scores

7.5Grafana LabsCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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