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CVE-2021-34781— Cisco Firepower Threat Defense Software SSH Connections Denial of Service Vulnerability

Quick assessment

Affected
Cisco Cisco Adaptive Security Appliance (ASA) Software
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Cisco Firepower Threat Defense（FTD）是美国思科（Cisco）公司的一套提供下一代防火墙服务的统一软件。 Cisco Firepower Threat Defense Software 存在缓冲区错误漏洞，该漏洞源于在无法建立 SSH 会话时缺乏正确的错误处理。攻击者可以通过向实例发送高频率的精心设计的 SSH 连接来利用此漏洞。成功的利用可能允许攻击者造成资源耗尽，从而导致受影响设备出现 DoS 条件。必须手动重新加载设备才能恢复。

CVSS 8.6 · High EPSS 1.39% · P71
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I. Basic Information for CVE-2021-34781

Vulnerability Information
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Vulnerability Title
Cisco Firepower Threat Defense Software SSH Connections Denial of Service Vulnerability
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
内存缓冲区边界内操作的限制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Cisco Firepower Threat Defense 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cisco Firepower Threat Defense（FTD）是美国思科（Cisco）公司的一套提供下一代防火墙服务的统一软件。 Cisco Firepower Threat Defense Software 存在缓冲区错误漏洞，该漏洞源于在无法建立 SSH 会话时缺乏正确的错误处理。攻击者可以通过向实例发送高频率的精心设计的 SSH 连接来利用此漏洞。成功的利用可能允许攻击者造成资源耗尽，从而导致受影响设备出现 DoS 条件。必须手动重新加载设备才能恢复。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Cisco Cisco Adaptive Security Appliance (ASA) Software n/a -

II. Public POCs for CVE-2021-34781

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III. Intelligence Information for CVE-2021-34781

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Vendor Advisories for CVE-2021-34781 (1)

Same Patch Batch · Cisco · 2021-10-27 · 20 CVEs total

CVE-2021-40117 8.6 HIGH Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software SSL/TLS D
CVE-2021-40116 8.6 HIGH Multiple Cisco Products Snort Rule Denial of Service Vulnerability
CVE-2021-40118 8.6 HIGH Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Web Servi
CVE-2021-34793 8.6 HIGH Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Transpare
CVE-2021-34792 8.6 HIGH Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Resource
CVE-2021-34783 8.6 HIGH Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Software-
CVE-2021-34762 8.1 HIGH Cisco Firepower Management Center Software Authenticated Directory Traversal Vulnerability
CVE-2021-40114 6.8 MEDIUM Multiple Cisco Products Snort Memory Leak Denial of Service Vulnerability
CVE-2021-34755 6.7 MEDIUM Cisco Firepower Threat Defense Software Command Injection Vulnerabilities
CVE-2021-34756 6.7 MEDIUM Cisco Firepower Threat Defense Software Command Injection Vulnerabilities
CVE-2021-34754 5.8 MEDIUM Cisco Firepower Threat Defense Software Ethernet Industrial Protocol Policy Bypass Vulnera
CVE-2021-40125 5.3 MEDIUM Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software IKEv2 Sit
CVE-2021-34787 5.3 MEDIUM Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Identity-
CVE-2021-34794 5.3 MEDIUM Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software SNMP Acce
CVE-2021-34763 4.8 MEDIUM Cisco Firepower Management Center Software Cross-Site Scripting and Open Redirect Vulnerab
CVE-2021-34764 4.8 MEDIUM Cisco Firepower Management Center Software Cross-Site Scripting and Open Redirect Vulnerab
CVE-2021-34790 4.7 MEDIUM Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Applicati
CVE-2021-34791 4.7 MEDIUM Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Applicati
CVE-2021-34761 4.4 MEDIUM Cisco Firepower Threat Defense Software CLI Arbitrary File Write Vulnerability

IV. Related Vulnerabilities

Same product: Cisco Adaptive Security Appliance (ASA) Software
Same vendor: Cisco
Same weakness: CWE-119

V. Comments for CVE-2021-34781

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