# CVE-2026-21729: Loki detected_fields query limits results in unbounded memory allocation

> Attackers can cause service unavailability in Grafana Loki by sending queries with large limits that trigger unbounded memory allocations.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Jul 2026
- **Updated:** 27 Aug 2026
- **Also known as:** GHSA-65p5-8cm9-qcxx, MINI-24x5-3xmm-qxhh, MINI-5v43-gwj7-p3hv, MINI-8qgg-j26m-93qx, MINI-jc2w-v5w6-pjvp

## What is CVE-2026-21729?

CVE-2026-21729 is a high-severity denial of service vulnerability in Grafana Loki, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Loki queries with large limits can cause large memory allocations which can impact the availability of the service, depending on its deployment strategy.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-21729?


## How do I fix CVE-2026-21729?

Upgrade to a fixed version.

## Is CVE-2026-21729 being exploited?

There is no known exploitation of CVE-2026-21729 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-21729 and fix it if it is affected.

What it is: CVE-2026-21729 is a high-severity denial of service vulnerability in Grafana Loki, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-21729 in the wild and no public exploit code.

Affected product: Grafana Loki. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-21729/ (Markdown: https://insights.sbomify.com/CVE-2026-21729/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-21729
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21729
- OSV: https://osv.dev/vulnerability/CVE-2026-21729

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-21729/
Summaries are generated and may contain mistakes; the official description above is the record.