HighFix available
strongswan — security advisory
The in-memory certificate cache in strongSwan before 5.9.4 has a remote integer overflow upon receiving many requests with different certificates to fill the cache and later trigger the replacement of cache entries. The code attempts to select a less-often-used cache entry by means of a random number generator, but this is not done correctly. Remote code execution might be a slight possibility.
- Products
- strongswan
- Affected versions
- Not specified
- Fixed versions
- 5.8.4-r3, 5.9.1-r1, 5.9.1-r2, 5.9.1-r3
- CVEs
- CVE-2021-41991
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 22:06 UTC · Revision 1
Source evidence
The in-memory certificate cache in strongSwan before 5.9.4 has a remote integer overflow upon receiving many requests with different certificates to fill the cache and later trigger the replacement of cache entries. The code attempts to select a less-often-used cache entry by means of a random number generator, but this is not done correctly. Remote code execution might be a slight possibility.
osv:ALPINE-CVE-2021-41991
strongswan
Fixed versions: 5.8.4-r3
strongswan
Fixed versions: 5.9.1-r1
strongswan
Fixed versions: 5.9.1-r2
strongswan
Fixed versions: 5.9.1-r3
strongswan
Fixed versions: 5.9.1-r3
strongswan
Fixed versions: 5.9.1-r3
strongswan
Fixed versions: 5.9.1-r3
strongswan
Fixed versions: 5.9.1-r3
strongswan
Fixed versions: 5.9.1-r3
strongswan
Fixed versions: 5.9.1-r3
strongswan
Fixed versions: 5.9.1-r3
strongswan
Fixed versions: 5.9.1-r3
strongswan
Fixed versions: 5.9.1-r3
Complete source record
{
"id": "36b113adc7c98a638ab42c8242799cce980f57c21bdb31bc3ec1550c51ed4b6f",
"url": "https://osv.dev/vulnerability/ALPINE-CVE-2021-41991",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "ALPINE-CVE-2021-41991",
"summary": "The in-memory certificate cache in strongSwan before 5.9.4 has a remote integer overflow upon receiving many requests with different certificates to fill the cache and later trigger the replacement of cache entries. The code attempts to select a less-often-used cache entry by means of a random number generator, but this is not done correctly. Remote code execution might be a slight possibility.",
"evidence": "osv:ALPINE-CVE-2021-41991",
"products": [
{
"name": {
"value": "strongswan",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.8.4-r3",
"evidence": "/affected/0/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "strongswan",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.9.1-r1",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": []
},
{
"name": {
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},
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"evidence": "/affected/2/ranges"
}
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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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"evidence": "/affected/4/ranges"
}
],
"affected_versions": []
},
{
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"evidence": "/affected/5/package/name"
},
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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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},
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{
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"evidence": "/affected/7/ranges"
}
],
"affected_versions": []
},
{
"name": {
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"evidence": "/affected/8/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.9.1-r3",
"evidence": "/affected/8/ranges"
}
],
"affected_versions": []
},
{
"name": {
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"evidence": "/affected/9/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.9.1-r3",
"evidence": "/affected/9/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "strongswan",
"evidence": "/affected/10/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.9.1-r3",
"evidence": "/affected/10/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "strongswan",
"evidence": "/affected/11/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.9.1-r3",
"evidence": "/affected/11/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "strongswan",
"evidence": "/affected/12/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.9.1-r3",
"evidence": "/affected/12/ranges"
}
],
"affected_versions": []
}
],
"severity": "high",
"structured": {
"id": "ALPINE-CVE-2021-41991",
"aliases": [
"ALPINE-CVE-2021-41991"
],
"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": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "4.2.10"
},
{
"fixed": "5.8.4-r3"
}
]
}
],
"package": {
"name": "strongswan",
"purl": "pkg:apk/alpine/strongswan?arch=source",
"ecosystem": "Alpine:v3.12"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-41991.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "4.2.10"
},
{
"fixed": "5.9.1-r1"
}
]
}
],
"package": {
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"purl": "pkg:apk/alpine/strongswan?arch=source",
"ecosystem": "Alpine:v3.13"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-41991.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
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"events": [
{
"introduced": "4.2.10"
},
{
"fixed": "5.9.1-r2"
}
]
}
],
"package": {
"name": "strongswan",
"purl": "pkg:apk/alpine/strongswan?arch=source",
"ecosystem": "Alpine:v3.14"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-41991.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
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"events": [
{
"introduced": "4.2.10"
},
{
"fixed": "5.9.1-r3"
}
]
}
],
"package": {
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"ecosystem": "Alpine:v3.15"
},
"database_specific": {
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{
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],
"package": {
"name": "strongswan",
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"ecosystem": "Alpine:v3.16"
},
"database_specific": {
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{
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"package": {
"name": "strongswan",
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"ecosystem": "Alpine:v3.17"
},
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{
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],
"package": {
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"purl": "pkg:apk/alpine/strongswan?arch=source",
"ecosystem": "Alpine:v3.18"
},
"database_specific": {
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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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],
"package": {
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"ecosystem": "Alpine:v3.23"
},
"database_specific": {
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},
{
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{
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},
{
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}
]
}
],
"package": {
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"ecosystem": "Alpine:v3.24"
},
"database_specific": {
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},
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}
],
"modified": "2026-10-23T17:17:56.217211768Z",
"provider": "osv",
"upstream": [
"CVE-2021-41991"
],
"references": [
"https://security.alpinelinux.org/vuln/CVE-2021-41991"
]
},
"related_cves": [
{
"value": "CVE-2021-41991",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 415570,
"published_at": "2021-10-18T14:15:10.333+00:00"
}