CVE-2021-34737— Cisco IOS XR Software DHCP Version 4 Server Denial of Service Vulnerability
Quick assessment
Affected
Cisco Cisco IOS XR 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 IOS XR是美国思科（Cisco）公司的一套为其网络设备开发的操作系统。 Cisco IOS XR软件的DHCP服务器功能(DHCPv4版本)存在代码问题漏洞，该漏洞源于某些DHCPv4消息在受影响的设备处理时未经正确验证。攻击者可利用该漏洞通过向受影响的设备发送格式错误的DHCPv4消息导致空指针解引用，从而导致系统崩溃
Possible ATT&CK Techniques 1 AI
T1499.002 · Service Exhaustion Flood
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I. Basic Information for CVE-2021-34737
Vulnerability Information
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Vulnerability Title
Cisco IOS XR Software DHCP Version 4 Server Denial of Service Vulnerability
Source: CVE Program / CVE List V5
Vulnerability Description
A vulnerability in the DHCP version 4 (DHCPv4) server feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to trigger a crash of the dhcpd process, resulting in a denial of service (DoS) condition. This vulnerability exists because certain DHCPv4 messages are improperly validated when they are processed by an affected device. An attacker could exploit this vulnerability by sending a malformed DHCPv4 message to an affected device. A successful exploit could allow the attacker to cause a NULL pointer dereference, resulting in a crash of the dhcpd process. While the dhcpd process is restarting, which may take up to approximately two minutes, DHCPv4 server services are unavailable on the affected device. This could temporarily prevent network access to clients that join the network during that time period. Note: Only the dhcpd process crashes and eventually restarts automatically. The router does not reload.
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:L
Source: CVE Program / CVE List V5
Vulnerability Type
空指针解引用
Source: CVE Program / CVE List V5
Vulnerability Title
Cisco IOS XR 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cisco IOS XR是美国思科（Cisco）公司的一套为其网络设备开发的操作系统。 Cisco IOS XR软件的DHCP服务器功能(DHCPv4版本)存在代码问题漏洞，该漏洞源于某些DHCPv4消息在受影响的设备处理时未经正确验证。攻击者可利用该漏洞通过向受影响的设备发送格式错误的DHCPv4消息导致空指针解引用，从而导致系统崩溃
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 IOS XR Software | n/a | - |
|
II. Public POCs for CVE-2021-34737
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Advisories for CVE-2021-34737 (1)
-
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-dhcp-dos-pjPVReLU vendor-advisory x_refsource_CISCO
Same Patch Batch · Cisco · 2021-09-09 · 13 CVEs total
| CVE-2021-34720 | 8.6 HIGH | Cisco IOS XR Software IP Service Level Agreements and Two-Way Active Measurement Protocol |
| CVE-2021-34718 | 8.1 HIGH | Cisco IOS XR Software Arbitrary File Read and Write Vulnerability |
| CVE-2021-34728 | 7.8 HIGH | Cisco IOS XR Software Authenticated User Privilege Escalation Vulnerabilities |
| CVE-2021-34719 | 7.8 HIGH | Cisco IOS XR Software Authenticated User Privilege Escalation Vulnerabilities |
| CVE-2021-34713 | 7.4 HIGH | Cisco IOS XR Software for ASR 9000 Series Routers Denial of Service Vulnerability |
| CVE-2021-34722 | 6.7 MEDIUM | Cisco IOS XR Software Command Injection Vulnerabilities |
| CVE-2021-34721 | 6.7 MEDIUM | Cisco IOS XR Software Command Injection Vulnerabilities |
| CVE-2021-34786 | 6.5 MEDIUM | Cisco BroadWorks CommPilot Application Software Vulnerabilities |
| CVE-2021-34785 | 6.5 MEDIUM | Cisco BroadWorks CommPilot Application Software Vulnerabilities |
| CVE-2021-34709 | 6.0 MEDIUM | Cisco IOS XR Software for Cisco 8000 and Network Convergence System 540 Series Routers Ima |
| CVE-2021-34708 | 6.0 MEDIUM | Cisco IOS XR Software for Cisco 8000 and Network Convergence System 540 Series Routers Ima |
| CVE-2021-34771 | 5.5 MEDIUM | Cisco IOS XR Software Unauthorized Information Disclosure Vulnerability |
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V. Comments for CVE-2021-34737
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