Security readout for executives and security teams
Plain-English summary
This is an unauthenticated availability flaw in Grafana’s avatar handling. Repeated uncached avatar requests can leave background work stuck, steadily consuming memory until Grafana may crash. The bundle rates impact as high because no login or user interaction is required and the result is service disruption, not data theft.
Executive priority
Prioritize externally exposed Grafana services because the issue can crash monitoring dashboards without authentication. Treat this as an availability risk requiring prompt vendor-version confirmation and remediation planning.
Technical view
For uncached /avatar/:hash requests, Grafana starts a refresh goroutine. If queued work exceeds the three-second handler timeout, the handler stops receiving while the goroutine later sends on an unbuffered channel, blocking permanently. Sustained random hashes can grow goroutines linearly and exhaust memory.
Likely exposure
Most concern is for Grafana or Grafana Enterprise instances reachable by untrusted users, especially internet-facing deployments. The provided affected metadata is duplicated and internally limited, so exact version exposure should be confirmed against Grafana’s advisory and Red Hat status.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation evidence. Exploitation requires sustained unauthenticated request volume to the avatar endpoint, causing resource exhaustion rather than confidentiality or integrity compromise.
Researcher notes
Evidence supports a goroutine leak caused by timeout handling around avatar refresh results. The bundle does not provide a specific fixed version, patch commit, or confirmed exploitation. Affected-version data appears repetitive and should not be treated as complete without vendor confirmation.
Mitigation direction
- Check Grafana’s advisory for affected and fixed versions before changing production systems.
- Apply the vendor-recommended update or mitigation once confirmed for your deployment.
- Reduce untrusted access to public Grafana endpoints where business requirements allow.
- Monitor memory and goroutine growth; restart degraded instances as an operational recovery measure.
Validation and detection
- Inventory Grafana OSS and Enterprise instances, including externally reachable deployments.
- Compare installed versions against Grafana’s advisory and Red Hat CVE/VEX records.
- Review access logs for unusual volume of randomized avatar requests and timeout patterns.
- Check runtime telemetry for sustained goroutine growth or memory pressure.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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CWE-400: Exact CWE lookup
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Open ATT&CK lookupCWE-703: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-772: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-21720 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6GRAFANACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADPVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- ADP timelineredhat-SADP
Made public.
- CVE publishedCVE Program
The CVE record was published.
- ADP timelineredhat-SADP
Reported to Red Hat.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-01-27T10:01:10.677Z: Reported to Red Hat.
- 2026-01-27T09:07:04.758Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://grafana.com/security/security-advisories/cve-2026-21720CVE reference, GRAFANA · vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-21720CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2433226CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-21720.jsonCVE reference, redhat-SADP · x_sadp-csaf-vex
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.