CVE-2026-21720
Description
A flaw was found in Grafana. A remote attacker can exploit this vulnerability by sending a sustained volume of uncached /avatar/:hash requests. This action causes the system to create and block goroutines, which are lightweight concurrent functions, leading to a continuous increase in memory usage. Over time, this resource exhaustion can cause Grafana to crash, resulting in a Denial of Service (DoS).
Statement
This IMPORTANT denial of service vulnerability in Grafana allows an unauthenticated attacker to exhaust system resources. By sending sustained requests to the /avatar/:hash endpoint, goroutines leak due to timed-out Gravatar image refreshes, leading to memory exhaustion and potential Grafana service crashes. This affects Grafana instances shipped with Red Hat Ceph Storage, Red Hat Enterprise Linux, and Red Hat In-Vehicle OS.
Mitigation
To mitigate this issue, disable Gravatar support in the Grafana configuration. Edit the `grafana.ini` file and set `allow_gravatar = false` under the `[users]` section. After modifying the configuration, restart the Grafana service for the changes to take effect. This action will prevent user avatars from being displayed.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (Other); DoS: Resource Consumption (Memory); DoS: Resource Consumption (CPU)
An attacker that can influence the allocation of resources that are not properly released could deplete the available resource pool and prevent all other processes from accessing the same type of resource. Frequently-affected resources include memory, CPU, disk space, power or battery, etc.
Frequently Asked Questions
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