UBUNTU-CVE-2021-34749 (CVE-2021-34749)
Vulnerability from osv_ubuntu – Published: 2021-08-18 20:15 – Updated: 2025-10-24 04:50 – Source website
VLAI
Details
A vulnerability in Server Name Identification (SNI) request filtering of Cisco Web Security Appliance (WSA), Cisco Firepower Threat Defense (FTD), and the Snort detection engine could allow an unauthenticated, remote attacker to bypass filtering technology on an affected device and exfiltrate data from a compromised host. This vulnerability is due to inadequate filtering of the SSL handshake. An attacker could exploit this vulnerability by using data from the SSL client hello packet to communicate with an external server. A successful exploit could allow the attacker to execute a command-and-control attack on a compromised host and perform additional data exfiltration attacks.
Severity
5.8 (Medium)
8.6 (High)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "snort",
"binary_version": "2.9.6.0-0ubuntu1"
},
{
"binary_name": "snort-common",
"binary_version": "2.9.6.0-0ubuntu1"
},
{
"binary_name": "snort-common-libraries",
"binary_version": "2.9.6.0-0ubuntu1"
},
{
"binary_name": "snort-rules-default",
"binary_version": "2.9.6.0-0ubuntu1"
}
]
},
"package": {
"ecosystem": "Ubuntu:14.04:LTS",
"name": "snort",
"purl": "pkg:deb/ubuntu/snort@2.9.6.0-0ubuntu1?arch=source\u0026distro=trusty"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.9.2.2-3",
"2.9.5.3-3",
"2.9.6.0-0ubuntu1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "snort",
"binary_version": "2.9.7.0-5"
},
{
"binary_name": "snort-common",
"binary_version": "2.9.7.0-5"
},
{
"binary_name": "snort-common-libraries",
"binary_version": "2.9.7.0-5"
},
{
"binary_name": "snort-rules-default",
"binary_version": "2.9.7.0-5"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "snort",
"purl": "pkg:deb/ubuntu/snort@2.9.7.0-5?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.9.7.0-5"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "snort",
"binary_version": "2.9.7.0-5build1"
},
{
"binary_name": "snort-common",
"binary_version": "2.9.7.0-5build1"
},
{
"binary_name": "snort-common-libraries",
"binary_version": "2.9.7.0-5build1"
},
{
"binary_name": "snort-rules-default",
"binary_version": "2.9.7.0-5build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "snort",
"purl": "pkg:deb/ubuntu/snort@2.9.7.0-5build1?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.9.7.0-5",
"2.9.7.0-5build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "snort",
"binary_version": "2.9.7.0-5build1"
},
{
"binary_name": "snort-common",
"binary_version": "2.9.7.0-5build1"
},
{
"binary_name": "snort-common-libraries",
"binary_version": "2.9.7.0-5build1"
},
{
"binary_name": "snort-rules-default",
"binary_version": "2.9.7.0-5build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "snort",
"purl": "pkg:deb/ubuntu/snort@2.9.7.0-5build1?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.9.7.0-5build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "snort",
"binary_version": "2.9.15.1-6build1"
},
{
"binary_name": "snort-common",
"binary_version": "2.9.15.1-6build1"
},
{
"binary_name": "snort-common-libraries",
"binary_version": "2.9.15.1-6build1"
},
{
"binary_name": "snort-rules-default",
"binary_version": "2.9.15.1-6build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "snort",
"purl": "pkg:deb/ubuntu/snort@2.9.15.1-6build1?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.9.15.1-5",
"2.9.15.1-6",
"2.9.15.1-6build1"
]
}
],
"aliases": [],
"details": "A vulnerability in Server Name Identification (SNI) request filtering of Cisco Web Security Appliance (WSA), Cisco Firepower Threat Defense (FTD), and the Snort detection engine could allow an unauthenticated, remote attacker to bypass filtering technology on an affected device and exfiltrate data from a compromised host. This vulnerability is due to inadequate filtering of the SSL handshake. An attacker could exploit this vulnerability by using data from the SSL client hello packet to communicate with an external server. A successful exploit could allow the attacker to execute a command-and-control attack on a compromised host and perform additional data exfiltration attacks.",
"id": "UBUNTU-CVE-2021-34749",
"modified": "2025-10-24T04:50:24Z",
"published": "2021-08-18T20:15:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2021-34749"
},
{
"type": "REPORT",
"url": "https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sni-data-exfil-mFgzXqLN"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2021-34749"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2021-34749"
]
}
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
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vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
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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.
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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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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