GrafanaApplication
CVE-2026-21720
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedEvery 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceIn Grafana, every uncached /avatar/:hash request spawns a goroutine to refresh the Gravatar image through a worker queue limited to 10 slots. When the queue is full and the 3-second timeout expires, the handler stops listening on an unbuffered channel, but the goroutine remains blocked trying to send, causing a goroutine leak. Sustained traffic with random hashes exhausts memory and crashes Grafana.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
GrafanaApplication
>= 3.0.0, < 11.6.9>= 12.0.0, < 12.0.8>= 12.1.0, < 12.1.5>= 12.2.0, < 12.2.3= 12.3.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check Grafana versionRun `grafana-server -v` or check the grafana version in the UI at Server Admin > Stats, or read from /var/lib/grafana/grafana.db in the db_version tableAffected if The installed version falls outside the fixed versions: not 11.6.9+, 12.0.8+, 12.1.5+, 12.2.3+, or not 12.3.1+
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Verify Gravatar avatar provider is enabledCheck grafana.ini for `[avatar]` section with `provider = gravatar` or check the database: `SELECT * FROM setting WHERE key='avatars'` shows value 'gravatar'Affected if Gravatar is configured as the avatar provider (the vulnerability only applies to the Gravatar handler)
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Monitor goroutine count over timeUse Grafana's diagnostic endpoint: curl http://localhost:3000/api/debug/pprof/goroutine?debug=1 (if enabled) or monitor via `go tool pprof` against the pprof endpoint; observe if goroutine count grows linearly with /avatar/:hash requestsAffected if Goroutine count increases linearly or stays elevated after traffic to /avatar/:hash endpoints with varying hash values
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Check for worker queue saturationReview Grafana logs for timeout messages related to avatar worker queue or check if HTTP requests to /avatar/:hash are timing out when many unique hashes are requested rapidlyAffected if Requests to /avatar/:hash timeout or log worker queue saturation errors under normal traffic conditions
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Inspect memory growth patternMonitor the Grafana process memory usage over several hours under typical traffic; check for steady linear memory increase correlated with unique avatar hash requestsAffected if Memory usage grows linearly without plateauing, especially when serving many different avatar hashes
A user is affected if they run a vulnerable Grafana version with Gravatar as the avatar provider and observe goroutine/memory leaks under normal traffic to the avatar endpoint.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped11.6.912.0.812.1.5
Fix the goroutine leak by converting the unbuffered channel to a buffered channel or implementing proper context cancellation with non-blocking sends, and add monitoring/limits on queued avatar refreshes.
Grafana 11.6.9, 12.0.8, 12.1.5, or 12.2.3 (or later)
- 1. Backup the Grafana database (SQLite, MySQL, or PostgreSQL) and configuration files (grafana.ini, custom.ini) before upgrading
- 2. Identify your current Grafana version by running `grafana-server -v` or checking the UI at Server Admin > Stats
- 3. Stop the Grafana service: `sudo systemctl stop grafana-server` or `sudo service grafana-server stop`
- 4. For package-based installations (deb/rpm), update the repository and install: `sudo apt-get update && sudo apt-get install grafana` (Debian/Ubuntu) or `sudo yum update grafana` (RHEL/CentOS)
- 5. For Docker deployments, pull and run the fixed version: `docker pull grafana/grafana:12.2.3` and update your docker-compose or container runtime
- 6. Verify the new version installed correctly: `grafana-server -v` should show 11.6.9, 12.0.8, 12.1.5, or 12.2.3 (or later)
- 7. Start the Grafana service: `sudo systemctl start grafana-server` or `sudo service grafana-server start`
- 8. Verify the /avatar endpoint no longer leaks goroutines under load by monitoring goroutine count (e.g., via Grafana's /debug/pprof goroutine endpoint)
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Grafana
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,128.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-21720 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-21720 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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