CVE-2026-21720: Grafana denial of service via resource exhaustion in avatar cache

CVE-2026-21720 · Severity: high · CVSS 7.5 · Published 2026-01-27

Grafana is a popular platform used for monitoring and visualizing data. A flaw in how it handles user profile pictures (avatars) allows an unauthenticated attacker to crash the server by sending a flood of specific requests. This can lead to a total service outage, preventing teams from monitoring their infrastructure.

Technologies: Grafana Labs Grafana Enterprise. Vendors: Grafana Labs.

Quick answers

Is CVE-2026-21720 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-21720 being exploited in the wild.
How severe is CVE-2026-21720?
High severity, with a CVSS score of 7.5, published 27 January 2026.
Which products and versions are affected?
Grafana Labs Grafana Enterprise >=3.0.0, <11.6.9; >=12.0.0, <12.0.8; >=12.1.0, <12.1.5; >=12.2.0, <12.2.3; >=12.3.0, <12.3.1.
Is there a fix for CVE-2026-21720?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-21720 attacked?
It is attacked over the network, in a web application.
Am I affected by CVE-2026-21720?
Check whether you run Grafana Labs Grafana Enterprise at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A denial of service vulnerability exists in Grafana's avatar caching component. Every uncached request to the '/avatar/:hash' endpoint spawns a goroutine to refresh the image from Gravatar. If the refresh task remains in the 10-slot worker queue for more than three seconds, the handler times out and stops listening, causing the goroutine to block indefinitely on an unbuffered channel. An attacker can exploit this by sending sustained traffic with random hashes, leading to linear goroutine growth and eventual memory exhaustion. The issue is fixed in versions 11.6.9, 12.0.8, 12.1.5, 12.2.3, and 12.3.1.

Affected products

  • Grafana Labs Grafana >=3.0.0, <11.6.9; >=12.0.0, <12.0.8; >=12.1.0, <12.1.5; >=12.2.0, <12.2.3; >=12.3.0, <12.3.1
  • Grafana Labs Grafana Enterprise >=3.0.0, <11.6.9; >=12.0.0, <12.0.8; >=12.1.0, <12.1.5; >=12.2.0, <12.2.3; >=12.3.0, <12.3.1

Timeline

  • 2026-01-27: disclosed
  • 2026-01-27: advisory

References

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