High
Unauthenticated DoS: avatar cache leaks goroutines when /avatar/:hash requests time out
Type: advisorySources: OSV
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-21720
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 7 Nov 2026, 20:45 UTC · Revision 1
Source evidence
Unauthenticated DoS: avatar cache leaks goroutines when /avatar/:hash requests time out
core-osv · Original sourcePublished 27 Jan 2026, 09:07 UTC
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.
osv:CVE-2026-21720
Complete source record
{
"id": "98fe3ee890ac88e7f6f81146e3aa800eacd2a413d58d9cc6325f055212d3ab15",
"url": "https://osv.dev/vulnerability/CVE-2026-21720",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Unauthenticated DoS: avatar cache leaks goroutines when /avatar/:hash requests time out",
"summary": "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.",
"evidence": "osv:CVE-2026-21720",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-21720",
"aliases": [
"BIT-grafana-2026-21720",
"CVE-2026-21720"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/grafana/grafana",
"type": "GIT",
"events": [
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"introduced": "0"
},
{
"fixed": "723a1642e8f43947a8e0c4621face5b3d985e1d2"
},
{
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{
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{
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{
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},
{
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],
"database_specific": {
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"cpe": "cpe:2.3:a:grafana:grafana:*:*:*:*:-:*:*:*",
"range": [
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{
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],
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{
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{
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{
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{
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{
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],
"source": "CPE_RANGE"
},
{
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"source": "CPE_RANGE"
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{
"cpe": "cpe:2.3:a:grafana:grafana:*:*:*:*:-:*:*:*",
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"source": "CPE_RANGE"
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{
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{
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],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:grafana:grafana:12.3.0:*:*:*:-:*:*:*",
"range": [
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{
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}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:grafana:grafana:12.3.0:*:*:*:enterprise:*:*:*",
"range": [
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},
{
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],
"source": "CPE_STRING"
}
]
}
}
],
"versions": [
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"v12.0.7",
"v11.6.8",
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"v11.6.2",
"v11.6.0",
"pkg/promlib/v0.0.8",
"pkg/promlib/v0.0.7",
"pkg/promlib/v0.0.6",
"pkg/promlib/v0.0.5",
"pkg/promlib/v0.0.4",
"pkg/promlib/v0.0.3",
"pkg/promlib/v0.0.2",
"pkg/promlib/v0.0.1",
"pkg/util/xorm/v0.0.1",
"v0.0.1-test",
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"v0.0.0-cloud",
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],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-21720.json"
}
}
],
"modified": "2026-10-28T02:30:51.449203345Z",
"provider": "osv",
"references": [
"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-21720.json",
"https://access.redhat.com/security/cve/CVE-2026-21720",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/21xxx/CVE-2026-21720.json",
"https://grafana.com/security/security-advisories/cve-2026-21720",
"https://nvd.nist.gov/vuln/detail/CVE-2026-21720",
"https://bugzilla.redhat.com/show_bug.cgi?id=2433226"
],
"provider_metadata": {
"cna_assigner": "GRAFANA",
"unresolved_ranges": [
{
"extracted_events": [
{
"range": [
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"introduced": "3.0.0"
},
{
"fixed": "11.6.9"
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{
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{
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{
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{
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"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/21xxx/CVE-2026-21720.json"
}
},
"related_cves": [
{
"value": "CVE-2026-21720",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 520353,
"published_at": "2026-01-27T09:07:04.758+00:00"
}