HighFix available
nginx — security advisory
ALPACA is an application layer protocol content confusion attack, exploiting TLS servers implementing different protocols but using compatible certificates, such as multi-domain or wildcard certificates. A MiTM attacker having access to victim's traffic at the TCP/IP layer can redirect traffic from one subdomain to another, resulting in a valid TLS session. This breaks the authentication of TLS and cross-protocol attacks may be possible where the behavior of one protocol service may compromise the other at the application layer.
- Products
- nginx
- Affected versions
- Not specified
- Fixed versions
- 1.20.1-r1
- CVEs
- CVE-2021-3618
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 22:05 UTC · Revision 1
Source evidence
ALPACA is an application layer protocol content confusion attack, exploiting TLS servers implementing different protocols but using compatible certificates, such as multi-domain or wildcard certificates. A MiTM attacker having access to victim's traffic at the TCP/IP layer can redirect traffic from one subdomain to another, resulting in a valid TLS session. This breaks the authentication of TLS and cross-protocol attacks may be possible where the behavior of one protocol service may compromise the other at the application layer.
osv:ALPINE-CVE-2021-3618
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
nginx
Fixed versions: 1.20.1-r1
Complete source record
{
"id": "8b18e56c0640c41ed801e4f8dc04d3971d32d7a324a2fada3a16bfabf62a12e4",
"url": "https://osv.dev/vulnerability/ALPINE-CVE-2021-3618",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "ALPINE-CVE-2021-3618",
"summary": "ALPACA is an application layer protocol content confusion attack, exploiting TLS servers implementing different protocols but using compatible certificates, such as multi-domain or wildcard certificates. A MiTM attacker having access to victim's traffic at the TCP/IP layer can redirect traffic from one subdomain to another, resulting in a valid TLS session. This breaks the authentication of TLS and cross-protocol attacks may be possible where the behavior of one protocol service may compromise the other at the application layer.",
"evidence": "osv:ALPINE-CVE-2021-3618",
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"evidence": "/affected/0/package/name"
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"evidence": "/affected/0/ranges"
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{
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{
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{
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],
"affected_versions": []
}
],
"severity": "high",
"structured": {
"id": "ALPINE-CVE-2021-3618",
"aliases": [
"ALPINE-CVE-2021-3618"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
}
],
"affected": [
{
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"events": [
{
"introduced": "0"
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{
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}
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],
"package": {
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"purl": "pkg:apk/alpine/nginx?arch=source",
"ecosystem": "Alpine:v3.14"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-3618.json"
},
"ecosystem_specific": {}
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{
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"package": {
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"ecosystem": "Alpine:v3.15"
},
"database_specific": {
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},
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{
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"package": {
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"ecosystem": "Alpine:v3.16"
},
"database_specific": {
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},
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{
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],
"package": {
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"database_specific": {
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],
"package": {
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"database_specific": {
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"package": {
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"database_specific": {
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"package": {
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"ecosystem": "Alpine:v3.20"
},
"database_specific": {
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},
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},
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},
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}
],
"modified": "2026-10-23T17:17:56.199330427Z",
"provider": "osv",
"upstream": [
"CVE-2021-3618"
],
"references": [
"https://security.alpinelinux.org/vuln/CVE-2021-3618"
]
},
"related_cves": [
{
"value": "CVE-2021-3618",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 415492,
"published_at": "2022-03-23T20:15:09.833+00:00"
}