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CVE-2026-20011— Multiple Cisco Products Snort 3 SMTP MIME 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.

多个思科产品受到 Snort 3 中 SMTP MIME 解码器漏洞的影响，该漏洞可能允许未经认证的远程攻击者导致 Snort 3 检测引擎重启。 此漏洞源于在解析 SMTP 报头中的 MIME 字段时缺乏必要的错误检查。攻击者可通过已建立的连接发送精心构造的 SMTP 数据包，使其被 Snort 3 解析，从而利用该漏洞。成功利用后，攻击者可导致 Snort 3 检测引擎意外重启，进而引发拒绝服务（DoS）状态。

CVSS 5.8 · Medium

Possible ATT&CK Techniques 1 AI

T1499.005

Affected Version Matrix 266

VendorProduct Version RangeStatus
Cisco Cisco Open Source Snort3 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
3.1.9.0 affected
… +92 more rows
Cisco Cisco Secure Firewall Threat Defense (FTD) Software 7.0.0 affected
7.0.0.1 affected
7.0.1 affected
7.0.1.1 affected
7.0.2 affected
7.2.0 affected
7.0.2.1 affected
7.0.3 affected
… +51 more rows
Cisco Cisco UTD SNORT IPS Engine Software 3.17.1S affected
16.12.3 affected
Fuji-16.9.5 affected
16.12.4 affected
17.3.1a affected
16.6.6 affected
16.12.2 affected
Fuji-16.9.6 affected
… +99 more rows
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I. Basic Information for CVE-2026-20011

Vulnerability Information
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Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Multiple Cisco Products Snort 3 SMTP MIME Denial of Service Vulnerability
Source: CVE Program / CVE List V5
Vulnerability Description
Multiple Cisco products are affected by a vulnerability in the Snort 3 SMTP MIME Decoder that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart. This vulnerability is due to a lack of error checking when the MIME fields of the SMTP header are parsed. An attacker could exploit this vulnerability by sending crafted SMTP packets through an established connection to be parsed by Snort 3. A successful exploit could allow the attacker to cause a denial of service (DoS) condition when the Snort 3 Detection Engine unexpectedly restarts.
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
使用不正确的长度值访问缓冲区
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Cisco Cisco Open Source Snort3 3.1.2.0 -
Cisco Cisco Secure Firewall Threat Defense (FTD) Software 7.0.0 -
Cisco Cisco UTD SNORT IPS Engine Software 3.17.1S -

II. Public POCs for CVE-2026-20011

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III. Intelligence Information for CVE-2026-20011

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Vendor Advisories for CVE-2026-20011 (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-805

V. Comments for CVE-2026-20011

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