curl — security advisory
curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious server can use this in rare unfortunate circumstances to potentially reach remote code execution in the client. When libcurl at run-time sets up support for TLS 1.3 session tickets on a connection using OpenSSL, it stores pointers to the transfer in-memory object for later retrieval when a session ticket arrives. If the connection is used by multiple transfers (like with a reused HTTP/1.1 connection or multiplexed HTTP/2 connection) that first transfer object might be freed before the new session is established on that connection and then the function will access a memory buffer that might be freed. When using that memory, libcurl might even call a function pointer in the object, making it possible for a remote code execution if the server could somehow manage to get crafted memory content into the correct place in memory.
- Products
- curl
- Affected versions
- Not specified
- Fixed versions
- 7.77.0-r0
- CVEs
- CVE-2021-22901
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 22:02 UTC · Revision 1
Source evidence
curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious server can use this in rare unfortunate circumstances to potentially reach remote code execution in the client. When libcurl at run-time sets up support for TLS 1.3 session tickets on a connection using OpenSSL, it stores pointers to the transfer in-memory object for later retrieval when a session ticket arrives. If the connection is used by multiple transfers (like with a reused HTTP/1.1 connection or multiplexed HTTP/2 connection) that first transfer object might be freed before the new session is established on that connection and then the function will access a memory buffer that might be freed. When using that memory, libcurl might even call a function pointer in the object, making it possible for a remote code execution if the server could somehow manage to get crafted memory content into the correct place in memory.
osv:ALPINE-CVE-2021-22901
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
curl
Fixed versions: 7.77.0-r0
Complete source record
{
"id": "12d32056085fd675e42c76ae5eff6d63441414c95ebe9205c07af4d86a298be5",
"url": "https://osv.dev/vulnerability/ALPINE-CVE-2021-22901",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "ALPINE-CVE-2021-22901",
"summary": "curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious server can use this in rare unfortunate circumstances to potentially reach remote code execution in the client. When libcurl at run-time sets up support for TLS 1.3 session tickets on a connection using OpenSSL, it stores pointers to the transfer in-memory object for later retrieval when a session ticket arrives. If the connection is used by multiple transfers (like with a reused HTTP/1.1 connection or multiplexed HTTP/2 connection) that first transfer object might be freed before the new session is established on that connection and then the function will access a memory buffer that might be freed. When using that memory, libcurl might even call a function pointer in the object, making it possible for a remote code execution if the server could somehow manage to get crafted memory content into the correct place in memory.",
"evidence": "osv:ALPINE-CVE-2021-22901",
"products": [
{
"name": {
"value": "curl",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/0/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/3/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/4/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/5/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/5/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/6/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/6/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/7/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/7/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/8/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/8/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/9/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/9/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/10/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/10/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/11/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/11/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "curl",
"evidence": "/affected/12/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "7.77.0-r0",
"evidence": "/affected/12/ranges"
}
],
"affected_versions": []
}
],
"severity": "high",
"structured": {
"id": "ALPINE-CVE-2021-22901",
"aliases": [
"ALPINE-CVE-2021-22901"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.12"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.13"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.14"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.15"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.16"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.17"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.18"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.19"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.20"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.21"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.22"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.23"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.75.0"
},
{
"fixed": "7.77.0-r0"
}
]
}
],
"package": {
"name": "curl",
"purl": "pkg:apk/alpine/curl?arch=source",
"ecosystem": "Alpine:v3.24"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-22901.json"
},
"ecosystem_specific": {}
}
],
"modified": "2026-10-23T17:17:56.152122884Z",
"provider": "osv",
"upstream": [
"CVE-2021-22901"
],
"references": [
"https://security.alpinelinux.org/vuln/CVE-2021-22901"
]
},
"related_cves": [
{
"value": "CVE-2021-22901",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 415305,
"published_at": "2021-06-11T16:15:11.12+00:00"
}