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CVE-2026-20218— Cisco Secure Firewall Threat Defense Snort 3 Visual Basic for Applications Buffer Overflow Denial of Service Vulnerability

Quick assessment

Affected
Cisco Cisco Open Source Snort3
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.

思科多款产品中的 Snort 3 的 Visual Basic for Applications (VBA) 解压缩引擎存在一处漏洞，该漏洞可能允许未经身份验证的远程攻击者导致 Snort 3 检测引擎意外重启，从而引发拒绝服务（DoS）状态。 此漏洞源于 Snort 3 在解压缩由用户控制的 VBA 数据时，未执行适当的范围检查。攻击者可通过向目标设备的 Snort 3 检测引擎发送特制的 VBA 数据来利用该漏洞。成功利用后，攻击者可导致栈数据溢出，进而引发拒绝服务（DoS）状态。

CVSS 5.8 · Medium

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 186

VendorProduct Version RangeStatus
Cisco Cisco Open Source Snort3 3.12.2.0 affected
3.1.2.0 affected
3.1.3.0 affected
3.1.4.0 affected
3.1.5.0 affected
3.1.6.0 affected
3.1.7.0 affected
3.1.8.0 affected
… +97 more rows
Cisco Cisco Secure Firewall Threat Defense (FTD) Software 7.2.0 affected
7.2.0.1 affected
7.2.1 affected
7.3.0 affected
7.2.2 affected
7.2.3 affected
7.3.1 affected
7.2.4 affected
… +35 more rows
Cisco Cisco UTD SNORT IPS Engine Software 17.12.1a affected
17.12.2 affected
17.13.1a affected
17.12.3 affected
17.14.1a affected
17.12.4 affected
17.12.3a affected
17.15.1a affected
… +30 more rows
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I. Basic Information for CVE-2026-20218

Vulnerability Information
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Vulnerability Title
Cisco Secure Firewall Threat Defense Snort 3 Visual Basic for Applications Buffer Overflow Denial of Service Vulnerability
Source: CVE Program / CVE List V5
Vulnerability Description
A vulnerability in the Snort 3 Visual Basic for Applications (VBA) Decompression Engine of multiple Cisco products could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to improper range checking when Snort 3 decompresses VBA data, which is user controlled. An attacker could exploit this vulnerability by sending crafted VBA data to the Snort 3 Detection Engine of a targeted device. A successful exploit could allow the attacker to cause an overflow of stack data, which could result in a DoS condition.
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
栈缓冲区溢出
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Cisco Cisco Open Source Snort3 3.12.2.0 -
Cisco Cisco Secure Firewall Threat Defense (FTD) Software 7.2.0 -
Cisco Cisco UTD SNORT IPS Engine Software 17.12.1a -

II. Public POCs for CVE-2026-20218

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III. Intelligence Information for CVE-2026-20218

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Other References for CVE-2026-20218 (1)

Same Patch Batch · Cisco · 2026-10-21 · 34 CVEs total

CVE-2026-76466 9.8 CRITICAL Cisco Expressway Series Remote Code Execution Vulnerability
CVE-2026-76473 9.8 CRITICAL Cisco Unified Communications Products Hardening Release: October 2026 - Improper control o
CVE-2026-76474 9.8 CRITICAL Cisco Unified Communications Products Hardening Release: October 2026 - Improper Authentic
CVE-2026-76475 9.3 CRITICAL Cisco Unified Communications Products Hardening Release: October 2026 - Cross-site Scripti
CVE-2026-20043 9.0 CRITICAL Multiple Cisco Products Snort 3 Software Hardening Release: October 2026
CVE-2026-76477 8.8 HIGH Cisco Unified Communications Products Hardening Release: October 2026 - Injection Vulnerab
CVE-2026-76476 8.8 HIGH Cisco Unified Communications Products Hardening Release: October 2026 - Improper Input Val
CVE-2026-76478 8.8 HIGH Cisco Unified Communications Products Hardening Release: October 2026 - Improper Access Co
CVE-2026-76490 8.6 HIGH Cisco Expressway Series Software Hardening Release: October 2026 - Out-of-bounds Write Vul
CVE-2026-76524 7.8 HIGH Open Source Snort 3 Control Channel Socket Aribitrary Command Execution Vulnerability
CVE-2026-20291 7.8 HIGH Multiple Cisco Products Snort 3 Software Hardening Release: October 2026
CVE-2026-76479 7.8 HIGH Cisco Unified Communications Products Hardening Release: October 2026 - Path Traversal Vul
CVE-2026-76494 7.8 HIGH Cisco Expressway Series Software Hardening Release: October 2026 - Code Injection Vulnerab
CVE-2026-76495 7.8 HIGH Cisco Expressway Series Software Hardening Release: October 2026 - Incorrect Permission As
CVE-2026-76481 7.5 HIGH Cisco Unified Communications Products Hardening Release: October 2026 - Improper Check or
CVE-2026-76491 7.5 HIGH Cisco Expressway Series Software Hardening Release: October 2026 - Denial of Service Vulne
CVE-2026-76492 7.5 HIGH Cisco Expressway Series Software Hardening Release: October 2026 - NULL Pointer Vulnerabil
CVE-2026-76505 7.5 HIGH Cisco IOS XR Software for ASR 9000 Series Routers IPv4 Unicast Packets Denial of Service V
CVE-2026-76493 7.5 HIGH Cisco Expressway Series Software Hardening Release: October 2026 - Uncaught Exception Vuln
CVE-2026-20236 7.5 HIGH Multiple Cisco Products Snort 3 Software Hardening Release: October 2026

Showing top 20 of 34 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: Cisco Open Source Snort3
Same vendor: Cisco
Same weakness: CWE-121

V. Comments for CVE-2026-20218

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