HighFix available
putty — security advisory
PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response. This makes it easier for an attacker-controlled SSH server to present a later spoofed authentication prompt (that the attacker can use to capture credential data, and use that data for purposes that are undesired by the client user).
- Products
- putty
- Affected versions
- Not specified
- Fixed versions
- 0.76-r0
- CVEs
- CVE-2021-36367
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 22:05 UTC · Revision 1
Source evidence
PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response. This makes it easier for an attacker-controlled SSH server to present a later spoofed authentication prompt (that the attacker can use to capture credential data, and use that data for purposes that are undesired by the client user).
osv:ALPINE-CVE-2021-36367
putty
Fixed versions: 0.76-r0
putty
Fixed versions: 0.76-r0
putty
Fixed versions: 0.76-r0
putty
Fixed versions: 0.76-r0
putty
Fixed versions: 0.76-r0
putty
Fixed versions: 0.76-r0
putty
Fixed versions: 0.76-r0
putty
Fixed versions: 0.76-r0
putty
Fixed versions: 0.76-r0
Complete source record
{
"id": "999c257d7354e69bced80d53d0f8573ffd178a4dea1c594fbbdb4861fc6bc6ff",
"url": "https://osv.dev/vulnerability/ALPINE-CVE-2021-36367",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "ALPINE-CVE-2021-36367",
"summary": "PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response. This makes it easier for an attacker-controlled SSH server to present a later spoofed authentication prompt (that the attacker can use to capture credential data, and use that data for purposes that are undesired by the client user).",
"evidence": "osv:ALPINE-CVE-2021-36367",
"products": [
{
"name": {
"value": "putty",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "0.76-r0",
"evidence": "/affected/0/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "putty",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "0.76-r0",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "putty",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
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"evidence": "/affected/2/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "putty",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "0.76-r0",
"evidence": "/affected/3/ranges"
}
],
"affected_versions": []
},
{
"name": {
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"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [
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"evidence": "/affected/4/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "putty",
"evidence": "/affected/5/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
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"evidence": "/affected/5/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "putty",
"evidence": "/affected/6/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "0.76-r0",
"evidence": "/affected/6/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "putty",
"evidence": "/affected/7/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "0.76-r0",
"evidence": "/affected/7/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "putty",
"evidence": "/affected/8/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "0.76-r0",
"evidence": "/affected/8/ranges"
}
],
"affected_versions": []
}
],
"severity": "high",
"structured": {
"id": "ALPINE-CVE-2021-36367",
"aliases": [
"ALPINE-CVE-2021-36367"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "0.76-r0"
}
]
}
],
"package": {
"name": "putty",
"purl": "pkg:apk/alpine/putty?arch=source",
"ecosystem": "Alpine:v3.11"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-36367.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "0.76-r0"
}
]
}
],
"package": {
"name": "putty",
"purl": "pkg:apk/alpine/putty?arch=source",
"ecosystem": "Alpine:v3.12"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-36367.json"
},
"ecosystem_specific": {}
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{
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],
"package": {
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"purl": "pkg:apk/alpine/putty?arch=source",
"ecosystem": "Alpine:v3.13"
},
"database_specific": {
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},
"ecosystem_specific": {}
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{
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}
],
"package": {
"name": "putty",
"purl": "pkg:apk/alpine/putty?arch=source",
"ecosystem": "Alpine:v3.14"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-36367.json"
},
"ecosystem_specific": {}
},
{
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}
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}
],
"package": {
"name": "putty",
"purl": "pkg:apk/alpine/putty?arch=source",
"ecosystem": "Alpine:v3.15"
},
"database_specific": {
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},
"ecosystem_specific": {}
},
{
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],
"package": {
"name": "putty",
"purl": "pkg:apk/alpine/putty?arch=source",
"ecosystem": "Alpine:v3.16"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-36367.json"
},
"ecosystem_specific": {}
},
{
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"events": [
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],
"package": {
"name": "putty",
"purl": "pkg:apk/alpine/putty?arch=source",
"ecosystem": "Alpine:v3.17"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-36367.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
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"events": [
{
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},
{
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}
]
}
],
"package": {
"name": "putty",
"purl": "pkg:apk/alpine/putty?arch=source",
"ecosystem": "Alpine:v3.18"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-36367.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
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"events": [
{
"introduced": "0"
},
{
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}
]
}
],
"package": {
"name": "putty",
"purl": "pkg:apk/alpine/putty?arch=source",
"ecosystem": "Alpine:v3.19"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-36367.json"
},
"ecosystem_specific": {}
}
],
"modified": "2026-10-23T17:17:56.199952812Z",
"provider": "osv",
"upstream": [
"CVE-2021-36367"
],
"references": [
"https://security.alpinelinux.org/vuln/CVE-2021-36367"
]
},
"related_cves": [
{
"value": "CVE-2021-36367",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 415495,
"published_at": "2021-07-09T21:15:08.54+00:00"
}