# CVE-2026-21720: Unauthenticated DoS: avatar cache leaks goroutines when /avatar/:hash requests time out

> CVE-2026-21720: Unauthenticated DoS: avatar cache leaks goroutines when /avatar/:hash requests time out. CVSS 7.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-21720
Last updated: 2026-08-27T17:22:47Z

- Published: 2026-01-27 09:07 UTC · Updated: 2026-08-27 17:22 UTC · Assigner: GRAFANA
- CVSS: 7.5 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS: 0.69%, 53th percentile (scored 2026-10-25)
- CISA KEV: no

## Description

Every uncached /avatar/:hash request spawns a goroutine that refreshes the Gravatar image. If the refresh sits in the 10-slot worker queue longer than three seconds, the handler times out and stops listening for the result, so that goroutine blocks forever trying to send on an unbuffered channel. Sustained traffic with random hashes keeps tripping this timeout, so goroutine count grows linearly, eventually exhausting memory and causing Grafana to crash on some systems.

## Affected vendors and products

- Grafana: grafana/grafana
- Grafana: grafana/grafana-enterprise
- Red Hat: Red Hat Ceph Storage 7
- Red Hat: Red Hat Ceph Storage 8
- Red Hat: Red Hat Enterprise Linux 10
- Red Hat: Red Hat Enterprise Linux 8
- Red Hat: Red Hat Enterprise Linux 9

## Tracked companies

- [Grafana Cloud](https://rewindex.com/company/grafana-cloud.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-21720)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-21720)
- [https://grafana.com/security/security-advisories/cve-2026-21720](https://grafana.com/security/security-advisories/cve-2026-21720)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-21720 · Markdown: https://rewindex.com/cve/CVE-2026-21720.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-21720 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:15:13.301Z