CVE-2026-20074— Cisco IOS XR Software Multi-Instance Intermediate System-to-Intermediate System Denial of Service Vulnerability
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I. Basic Information for CVE-2026-20074
Vulnerability Information
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Vulnerability Title
Cisco IOS XR Software Multi-Instance Intermediate System-to-Intermediate System Denial of Service Vulnerability
Source: NVD (National Vulnerability Database)
Vulnerability Description
A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing feature of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause the IS-IS process to restart unexpectedly. This vulnerability is due to insufficient input validation of ingress IS-IS packets. An attacker could exploit this vulnerability by sending crafted IS-IS packets to an affected device after forming an adjacency. A successful exploit could allow the attacker to cause the IS-IS process to restart unexpectedly, resulting in a temporary loss of connectivity to advertised networks and a denial of service (DoS) condition. Note: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device and must have formed an adjacency.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
CWE-1287
Source: NVD (National Vulnerability Database)
Vulnerability Title
Cisco IOS XR 安全漏洞
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存在安全漏洞，该漏洞源于对入口IS-IS数据包的输入验证不足，可能导致IS-IS进程意外重启和拒绝服务。
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 | 7.8.1 | - |
II. Public POCs for CVE-2026-20074
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · Cisco · 2026-03-11 · 6 CVEs total
| CVE-2026-20040 | 8.8 HIGH | Cisco IOS XR Software CLI Privilege Escalation Vulnerability |
| CVE-2026-20046 | 8.8 HIGH | Cisco IOS XR Software CLI Privilege Escalation Vulnerability |
| CVE-2026-20118 | 6.8 MEDIUM | Cisco IOS-XR NCS 5500 and NCS 5700 Egress Packet Network Interfaces Aligner Interrupt Deni |
| CVE-2026-20116 | 6.1 MEDIUM | Multiple Cisco Contact Center Products Cross-Site Scripting Vulnerabilities |
| CVE-2026-20117 | 6.1 MEDIUM | Multiple Cisco Contact Center Products Cross-Site Scripting Vulnerabilities |
IV. Related Vulnerabilities
Same product: Cisco IOS XR Software
- CVE-2026-20118
Cisco IOS-XR NCS 5500 and NCS 5700 Egress Packet Network Int - CVE-2026-20046
Cisco IOS XR Software CLI Privilege Escalation Vulnerability - CVE-2026-20040
Cisco IOS XR Software CLI Privilege Escalation Vulnerability - CVE-2025-20340
Cisco IOS XR Address Resolution Protocol Broadcast Storm Vul - CVE-2025-20248
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Same weakness: CWE-1287
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V. Comments for CVE-2026-20074
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