Cisco Firepower Threat Defense Software SSH Connections Denial of Service Vulnerability
Summary
| CVE | CVE-2021-34781 |
|---|---|
| State | PUBLISHED |
| Assigner | cisco |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2021-10-27 19:15:08 UTC |
| Updated | 2026-08-11 19:33:44 UTC |
| Description | A vulnerability in the processing of SSH connections for multi-instance deployments of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on the affected device. This vulnerability is due to a lack of proper error handling when an SSH session fails to be established. An attacker could exploit this vulnerability by sending a high rate of crafted SSH connections to the instance. A successful exploit could allow the attacker to cause resource exhaustion, which causes a DoS condition on the affected device. The device must be manually reloaded to recover. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from [email protected]
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Problem Types: CWE-119 | CWE-755 | CWE-119 CWE-119
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | [email protected] | Secondary | 8.6 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
| 3.1 | CNA | DECLARED | 8.6 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
| 2.0 | [email protected] | Primary | 7.1 | AV:N/AC:M/Au:N/C:N/I:N/A:C |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v2.0 Breakdown
Access Vector
NetworkAccess Complexity
MediumAuthentication
NoneConfidentiality
NoneIntegrity
NoneAvailability
CompleteAV:N/AC:M/Au:N/C:N/I:N/A:C
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Cisco | Firepower Management Center Virtual Appliance | 6.3.0 | All | All | All |
| Application | Cisco | Firepower Management Center Virtual Appliance | 6.4.0 | All | All | All |
| Application | Cisco | Firepower Management Center Virtual Appliance | 6.4.0.13 | All | All | All |
| Application | Cisco | Firepower Management Center Virtual Appliance | 6.5.0 | All | All | All |
| Application | Cisco | Firepower Management Center Virtual Appliance | 6.6.0 | All | All | All |
| Application | Cisco | Firepower Management Center Virtual Appliance | 6.7.0.3 | All | All | All |
| Application | Cisco | Firepower Management Center Virtual Appliance | 6.7.1 | All | All | All |
| Application | Cisco | Firepower Management Center Virtual Appliance | 7.0.0 | All | All | All |
| Application | Cisco | Secure Firewall Threat Defense | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Cisco | Cisco Adaptive Security Appliance ASA Software | affected n/a | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| Cisco Firepower Threat Defense Software SSH Connections Denial of Service Vulnerability | af854a3a-2127-422b-91ae-364da2661108 | tools.cisco.com | Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
Additional Advisory Data
Exploits
CNA: The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
There are currently no legacy QID mappings associated with this CVE.