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CVE-2026-20281— Cisco Desk Phone 9800 Series, IP Phone 7800 and 8800 Series, and Video Phone 8875 with SIP Software Denial of Service Vulnerability

Quick assessment

Affected
Cisco Cisco Session Initiation Protocol (SIP) 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 Session Initiation Protocol Software是美国Cisco公司的一款支持会话发起协议的网络通信软件。 Cisco Session Initiation Protocol Software存在资源管理错误漏洞，该漏洞源于处理HTTP数据包时内存管理不当，可能导致未经身份验证的远程攻击者通过发送连续的特制HTTP数据包，使设备持续消耗内存，造成拒绝服务。

CVSS 7.5 · High EPSS 0.37% · P29

Possible ATT&CK Techniques 1 AI

T1999

Affected Version Matrix 110

VendorProduct Version RangeStatus
Cisco Cisco Session Initiation Protocol (SIP) Software 12.1(1)SR1 affected
11.5(1) affected
10.3(2) affected
10.2(2) affected
10.3(1) affected
10.3(1)SR4 affected
11.0(1) affected
10.4(1)SR2 3rd Party affected
… +102 more rows
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I. Basic Information for CVE-2026-20281

Vulnerability Information
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Vulnerability Title
Cisco Desk Phone 9800 Series, IP Phone 7800 and 8800 Series, and Video Phone 8875 with SIP Software Denial of Service Vulnerability
Source: CVE Program / CVE List V5
Vulnerability Description
A vulnerability in Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Series, and Cisco Video Phone 8875 that are running Cisco Session Initiation Protocol (SIP) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper memory management when an affected device processes HTTP packets. An attacker could exploit this vulnerability by sending a continuous stream of crafted HTTP packets to the device. A successful exploit could allow the attacker to cause the affected device to continuously consume memory, resulting in a DoS condition. A manual reboot of the device is required to recover from this condition. Note: For this vulnerability to be exploitable, the phone must be registered to Cisco Unified Communications Manager (Unified CM) and have Web Access enabled. Web Access is disabled by default.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
在移除最后引用时对内存的释放不恰当(内存泄露)
Source: CVE Program / CVE List V5
Vulnerability Title
Cisco Session Initiation Protocol Software 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cisco Session Initiation Protocol Software是美国Cisco公司的一款支持会话发起协议的网络通信软件。 Cisco Session Initiation Protocol Software存在资源管理错误漏洞，该漏洞源于处理HTTP数据包时内存管理不当，可能导致未经身份验证的远程攻击者通过发送连续的特制HTTP数据包，使设备持续消耗内存，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 Session Initiation Protocol (SIP) Software 12.1(1)SR1 -

II. Public POCs for CVE-2026-20281

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III. Intelligence Information for CVE-2026-20281

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Vendor Advisories for CVE-2026-20281 (1)

Same Patch Batch · Cisco · 2026-09-02 · 11 CVEs total

CVE-2026-20279 9.8 CRITICAL Cisco IOS XR Software Security Hardening Release: September 2026
CVE-2026-20274 9.8 CRITICAL Cisco IOS XR Software Security Hardening Release: September 2026
CVE-2026-20212 9.8 CRITICAL Cisco Nexus 3000 and 9000 Series Switches Silicon One Hardware Abstraction Layer Remote Co
CVE-2026-20280 8.8 HIGH Cisco IOS XR Software Security Hardening Release: September 2026
CVE-2026-20278 8.8 HIGH Cisco IOS XR Software Security Hardening Release: September 2026
CVE-2026-20275 8.8 HIGH Cisco IOS XR Software Security Hardening Release: September 2026
CVE-2026-20276 8.6 HIGH Cisco IOS XR Software Security Hardening Release: September 2026
CVE-2026-20277 8.2 HIGH Cisco IOS XR Software Security Hardening Release: September 2026
CVE-2026-20355 5.9 MEDIUM Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty
CVE-2026-20354 5.9 MEDIUM Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty

IV. Related Vulnerabilities

Same product: Cisco Session Initiation Protocol (SIP) Software
Same vendor: Cisco
Same weakness: CWE-401

V. Comments for CVE-2026-20281

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