CVE-2026-21720
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk46th percentile - higher than 46% of all known CVEs
Summary
The vulnerability in Grafana causes every uncached /avatar/:hash request to spawn a goroutine that refreshes the Gravatar image. If the refresh sits in the worker queue longer than three seconds, the handler times out and stops listening for the result, so the goroutine blocks forever trying to send on an unbuffered channel. Sustained traffic with random hashes keeps tripping this timeout, causing goroutine count to grow linearly, eventually exhausting memory and crashing Grafana on some systems.
Risk Assessment
The risk is a denial-of-service (DoS) attack by sending many /avatar/:hash requests with random hashes, leading to memory exhaustion and Grafana crash, disrupting monitoring and dashboard access.
Recommendation
Immediately upgrade Grafana to a patched version that fixes the goroutine blocking on the unbuffered channel and increases the timeout for /avatar/:hash requests. As a temporary workaround, restrict access to the /avatar/:hash endpoint or increase memory resources.
Other vulnerabilities in Grafana
See all- CVE-2026-17033Medium
An authenticated attacker with Editor access or alert.instances.external:write can submit an external Alertmanager alert containing a controlled generatorURL. Grafana renders alert.generatorURL directly as the Alert Details See source LinkButton href without URL-scheme sanitization or a safe-protocol allowlist. The click interceptor's :// heuristic can be bypassed by placing :// inside a JavaScript comment. When a user with read access clicks See source, the browser executes attacker-controlled JavaScript in the Grafana origin with the clicking user's permissions.
- CVE-2026-28381Critical
The Snowflake datasource vulnerability allows GET/PUT commands, enabling any user with query access to read/write files between the local Grafana server and the connected Snowflake host.
- CVE-2026-27876Critical
A chained attack via SQL Expressions and a Grafana Enterprise plugin can lead to remote arbitrary code execution (RCE). The vulnerability requires the sqlExpressions feature toggle to be enabled and affects specific Grafana OSS versions.
- CVE-2025-41115Critical
In Grafana versions 12.x where SCIM provisioning is enabled and configured, a vulnerability in user identity handling allows a malicious or compromised SCIM client to provision a user with a numeric externalId, which could allow overriding internal user IDs and lead to impersonation or privilege escalation.
- CVE-2023-3128Critical
Grafana validates Azure AD accounts based on the email claim. The email field in Azure AD profiles is not unique and can be easily modified, leading to account takeover and authentication bypass when Azure AD OAuth is configured with a multi-tenant app.
- CVE-2026-19197Medium
A user with organization administrator permissions can delete dashboard snapshots belonging to other organizations on the same Grafana instance, and can recover a snapshot's secret delete key using only its public share key (broken access control).
- CVE-2026-17183High
An authenticated user with permission to create or edit alert rules can bypass datasource query authorization by marking an alert rule query as a server-side expression while referencing a real datasource UID (incorrect authorization). This can expose data accessible through Grafana's configured datasource credentials to users who lack permission to query that datasource.
- CVE-2026-11817Medium
This vulnerability only affects Grafana stacks with multiple organizations. A user who is an Org Admin of one organization can call GET /api/access-control/users/permissions/search?actionPrefix=dashboards: and receive permission data from other organizations. Disclosed data is limited to dashboard/folder UIDs and permission mappings, not content or personal data.
- CVE-2026-21723Medium
The alertmanager templates test endpoint (/api/alertmanager/grafana/config/api/v1/templates/test) in Grafana can execute templates with no memory limits. Mass-executing templates in a short period causes OOM and crashes the Grafana service. The endpoint requires very low privileges and is exploitable with anonymous access enabled.
- CVE-2026-8609Medium
An unauthenticated attacker can repeatedly call Grafana's OAuth login route with unique values, causing unbounded memory growth that can eventually exhaust memory and crash the Grafana instance (denial of service).
Original NVD description (English source)
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.