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CVE-2026-20311— Cisco IOS XE Software Web UI Denial of Service Vulnerability

Quick assessment

Affected
Cisco Cisco IOS XE 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 XE Software是美国Cisco公司的一款管理网络设备的操作系统。 Cisco IOS XE Software 17.3.1版本至17.18.3a版本和26.1.1版本至26.2.1ea版本存在缓冲区错误漏洞，该漏洞源于基于Web的管理界面错误处理不足，可能允许低权限的已认证远程攻击者使用格式错误的证书进行身份验证，导致设备重新加载，造成拒绝服务。

CVSS 6.3 · Medium EPSS 0.25% · P15

Affected Version Matrix 152

VendorProduct Version RangeStatus
Cisco Cisco IOS XE Software 17.3.1 affected
17.3.1a affected
17.3.2a affected
17.3.1w affected
17.3.2 affected
17.4.1 affected
17.4.1a affected
17.3.1x affected
… +144 more rows
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I. Basic Information for CVE-2026-20311

Vulnerability Information
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Vulnerability Title
Cisco IOS XE Software Web UI Denial of Service Vulnerability
Source: CVE Program / CVE List V5
Vulnerability Description
A vulnerability in the web-based management interface of Cisco IOS XE Software could allow an authenticated, remote attacker with low privileges to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient error handling in the web-based management interface. An attacker could exploit this vulnerability by authenticating with a malformed certificate. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
缓冲区上溢读取
Source: CVE Program / CVE List V5
Vulnerability Title
Cisco IOS XE Software 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cisco IOS XE Software是美国Cisco公司的一款管理网络设备的操作系统。 Cisco IOS XE Software 17.3.1版本至17.18.3a版本和26.1.1版本至26.2.1ea版本存在缓冲区错误漏洞，该漏洞源于基于Web的管理界面错误处理不足，可能允许低权限的已认证远程攻击者使用格式错误的证书进行身份验证，导致设备重新加载，造成拒绝服务。
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 XE Software 17.3.1 -

II. Public POCs for CVE-2026-20311

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III. Intelligence Information for CVE-2026-20311

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Vendor Advisories for CVE-2026-20311 (1)

Same Patch Batch · Cisco · 2026-08-05 · 23 CVEs total

CVE-2026-20304 9.9 CRITICAL Cisco Catalyst SD-WAN Security Hardening Release - Access Control Vulnerabilities
CVE-2026-20303 9.9 CRITICAL Cisco Catalyst SD-WAN Security Hardening Release - Input Validation Vulnerabilities
CVE-2026-20272 9.8 CRITICAL Cisco IOS XE Software Security Hardening Release
CVE-2026-20310 9.1 CRITICAL Cisco SD-WAN Software Security Hardening Release - Improper Link Resolution Before File Ac
CVE-2026-20267 9.0 CRITICAL Cisco IOS XE Software Security Hardening Release
CVE-2026-20312 8.8 HIGH Cisco Catalyst SD-WAN Security Hardening Release - Information Disclosure Vulnerabilities
CVE-2026-20200 8.8 HIGH Cisco Integrated Management Controller Argument Injection and Remote Code Execution Vulner
CVE-2026-20263 8.6 HIGH Cisco IOS XE Software Blocks Extensible Exchange Protocol Denial of Service Vulnerability
CVE-2026-20268 8.6 HIGH Cisco IOS XE Software Security Hardening Release
CVE-2026-20269 8.6 HIGH Cisco IOS XE Software Security Hardening Release
CVE-2026-20270 8.6 HIGH Cisco IOS XE Software Security Hardening Release
CVE-2026-20271 8.6 HIGH Cisco IOS XE Software Security Hardening Release
CVE-2026-20273 8.6 HIGH Cisco IOS XE Software Security Hardening Release
CVE-2026-20301 8.6 HIGH Cisco IOS Software and IOS XE Software Extensible Messaging Client Protocol Denial of Serv
CVE-2026-20313 7.7 HIGH Cisco Catalyst SD-WAN Security Hardening Release - Memory Corruption Vulnerabilities
CVE-2026-20124 7.7 HIGH Cisco IOS XE Software SNMP Denial of Service Vulnerability
CVE-2026-20288 6.5 MEDIUM Cisco IMC Remote Code Execution Vulnerability Remote Code Execution Vulnerability
CVE-2026-20294 6.5 MEDIUM Cisco Catalyst SD-WAN Manager Information Disclosure Vulnerability
CVE-2026-20289 5.7 MEDIUM Cisco RoomOS Logging Subsystem Information Disclosure Vulnerability
CVE-2026-20028 5.0 MEDIUM Cisco Terminal Services Agent Firewall Rules Bypass Vulnerability

Showing top 20 of 23 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: Cisco IOS XE Software
Same vendor: Cisco
Same weakness: CWE-126

V. Comments for CVE-2026-20311

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