ubuntu-cve-2021-22901
Vulnerability from osv_ubuntu
Published
2021-05-26 06:00
Modified
2025-07-16 04:57
Summary
Details
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.
Severity
8.1 (High)
N/A (UNKNOWN)
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"ecosystem_specific": {
"availability": "No subscription required",
"binaries": [
{
"binary_name": "curl",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "curl-dbgsym",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl3-gnutls",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl3-gnutls-dbgsym",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl3-nss",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl3-nss-dbgsym",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl4",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl4-dbgsym",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl4-doc",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl4-gnutls-dev",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl4-nss-dev",
"binary_version": "7.58.0-2ubuntu3.13"
},
{
"binary_name": "libcurl4-openssl-dev",
"binary_version": "7.58.0-2ubuntu3.13"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "curl",
"purl": "pkg:deb/ubuntu/curl@7.58.0-2ubuntu3.13?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "7.58.0-2ubuntu3.13"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"7.55.1-1ubuntu2",
"7.55.1-1ubuntu2.1",
"7.57.0-1ubuntu1",
"7.58.0-2ubuntu1",
"7.58.0-2ubuntu2",
"7.58.0-2ubuntu3",
"7.58.0-2ubuntu3.1",
"7.58.0-2ubuntu3.2",
"7.58.0-2ubuntu3.3",
"7.58.0-2ubuntu3.5",
"7.58.0-2ubuntu3.6",
"7.58.0-2ubuntu3.7",
"7.58.0-2ubuntu3.8",
"7.58.0-2ubuntu3.9",
"7.58.0-2ubuntu3.10",
"7.58.0-2ubuntu3.12"
]
},
{
"ecosystem_specific": {
"availability": "No subscription required",
"binaries": [
{
"binary_name": "curl",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "curl-dbgsym",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl3-gnutls",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl3-gnutls-dbgsym",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl3-nss",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl3-nss-dbgsym",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl4",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl4-dbgsym",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl4-doc",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl4-gnutls-dev",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl4-nss-dev",
"binary_version": "7.68.0-1ubuntu2.5"
},
{
"binary_name": "libcurl4-openssl-dev",
"binary_version": "7.68.0-1ubuntu2.5"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "curl",
"purl": "pkg:deb/ubuntu/curl@7.68.0-1ubuntu2.5?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "7.68.0-1ubuntu2.5"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"7.65.3-1ubuntu3",
"7.65.3-1ubuntu4",
"7.66.0-1ubuntu1",
"7.67.0-2ubuntu1",
"7.68.0-1ubuntu1",
"7.68.0-1ubuntu2",
"7.68.0-1ubuntu2.1",
"7.68.0-1ubuntu2.2",
"7.68.0-1ubuntu2.4"
]
}
],
"aliases": [],
"details": "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.",
"id": "UBUNTU-CVE-2021-22901",
"modified": "2025-07-16T04:57:01Z",
"published": "2021-05-26T06:00:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2021-22901"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2021-22901"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2021-22901"
],
"withdrawn": "2025-07-18T16:46:39Z"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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