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CVE-2026-20179

Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities

MEDIUM
5.8
CVSS Score
Published: October 21, 2026 at 04:12 PM UTC
Updated: October 22, 2026 at 07:11 PM UTC
3 products affected across 1 vendorSecure Firewall Threat DefenseUnified Threat Defense Snort Intrusion Prevention System EngineCisco Open Source Snort3

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Severity
MEDIUM5.8
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

Description

Multiple Cisco products are affected by a vulnerability in the Snort 3 Generic Routing Encapsulation (GRE) Detection Engine that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart, resulting in an interruption of packet inspection. This vulnerability is due to incomplete error checking when Snort 3 parses GRE packets. An attacker could exploit this vulnerability by sending a crafted GRE packet to a targeted device to be parsed by Snort. A successful exploit could allow the attacker to cause the Snort 3 Detection Engine to restart unexpectedly, resulting in a DoS condition.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Cisco Open Source Snort3· Cisco
90%
3.1.10.03.1.12.03.1.13.03.1.14.03.1.15.03.1.16.03.1.17.03.1.18.03.1.19.03.1.2.03.1.20.03.1.21.03.1.22.03.1.23.03.1.24.03.1.25.03.1.27.03.1.28.03.1.29.03.1.3.03.1.30.03.1.31.03.1.32.03.1.36.03.1.38.03.1.39.03.1.4.03.1.40.03.1.41.03.1.42.03.1.43.03.1.45.03.1.47.03.1.48.03.1.5.03.1.50.03.1.51.03.1.52.03.1.53.03.1.55.03.1.56.03.1.57.03.1.58.03.1.59.03.1.6.03.1.60.03.1.61.03.1.62.03.1.63.03.1.64.03.1.65.03.1.66.03.1.67.03.1.69.03.1.7.03.1.70.03.1.71.03.1.72.03.1.73.03.1.74.03.1.75.03.1.76.03.1.77.03.1.78.03.1.8.03.1.81.03.1.82.03.1.83.03.1.84.03.1.9.03.10.0.03.10.1.03.10.2.03.11.1.03.12.1.03.12.2.03.2.1.03.2.2.03.3.0.03.3.1.03.3.2.03.3.3.03.3.4.03.3.5.03.3.7.03.5.0.03.5.1.03.5.2.03.6.0.03.6.1.03.6.2.03.6.3.03.7.0.03.7.1.03.7.2.03.7.3.03.7.4.03.8.1.03.9.0.03.9.1.03.9.2.03.9.3.03.9.5.03.9.6.03.9.7.0
Secure Firewall Threat Defense· Cisco
90%
10.0.07.0.07.0.0.17.0.17.0.1.17.0.27.0.2.17.0.37.0.47.0.57.0.67.0.6.17.0.6.27.0.6.37.0.77.0.87.0.8.17.0.97.2.07.2.0.17.2.17.2.107.2.10.27.2.117.2.27.2.37.2.47.2.4.17.2.57.2.5.17.2.5.27.2.67.2.77.2.87.2.8.17.2.97.3.07.3.17.3.1.17.3.1.27.4.07.4.17.4.1.17.4.27.4.2.17.4.2.27.4.2.37.4.2.47.4.37.4.47.4.77.6.07.6.17.6.27.6.2.17.6.47.7.07.7.107.7.10.17.7.11
Unified Threat Defense Snort Intrusion Prevention System Engine· Cisco
90%
17.12.1a17.12.217.12.317.12.3a17.12.417.12.4a17.12.4b17.12.517.12.5a17.12.5b17.12.5c17.12.5d17.12.617.12.717.12.7a17.12.7b17.12.817.13.1a17.14.1a17.15.1a17.15.2a17.15.2c17.15.317.15.3a17.15.417.15.4c17.15.517.15.5a17.15.617.16.1a17.17.117.18.117.18.1a17.18.217.18.3a17.18.426.1.126.1.2

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (1)

Source: cverecord
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-misc-dos-6mB22qAK

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.8MEDIUMcisco
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
NONE
Integrity
NONE
Availability
LOW
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-128

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