CVE-2026-20179
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Snort 3 GRE Packet Parsing DoS Vulnerability
Vulnerability report for CVE-2026-20179, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-21
Last updated on: 2026-10-21
Assigner: Cisco Systems, Inc.
Description
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.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| Cisco | Cisco | Open Source Snort3 3.12.2.0 |
| Cisco | Cisco | Open Source Snort3 3.1.2.0 |
| Cisco | Cisco | Open Source Snort3 3.1.3.0 |
| Cisco | Cisco | Open Source Snort3 3.1.4.0 |
| Cisco | Cisco | Open Source Snort3 3.1.5.0 |
| Cisco | Cisco | Open Source Snort3 3.1.6.0 |
| Cisco | Cisco | Open Source Snort3 3.1.7.0 |
| Cisco | Cisco | Open Source Snort3 3.1.8.0 |
| Cisco | Cisco | Open Source Snort3 3.1.9.0 |
| Cisco | Cisco | Open Source Snort3 3.1.10.0 |
| Cisco | Cisco | Open Source Snort3 3.1.12.0 |
| Cisco | Cisco | Open Source Snort3 3.1.13.0 |
| Cisco | Cisco | Open Source Snort3 3.1.14.0 |
| Cisco | Cisco | Open Source Snort3 3.1.15.0 |
| Cisco | Cisco | Open Source Snort3 3.1.16.0 |
| Cisco | Cisco | Open Source Snort3 3.1.17.0 |
| Cisco | Cisco | Open Source Snort3 3.1.18.0 |
| Cisco | Cisco | Open Source Snort3 3.1.19.0 |
| Cisco | Cisco | Open Source Snort3 3.1.20.0 |
| Cisco | Cisco | Open Source Snort3 3.1.21.0 |
| Cisco | Cisco | Open Source Snort3 3.1.22.0 |
| Cisco | Cisco | Open Source Snort3 3.1.23.0 |
| Cisco | Cisco | Open Source Snort3 3.1.24.0 |
| Cisco | Cisco | Open Source Snort3 3.1.25.0 |
| Cisco | Cisco | Open Source Snort3 3.1.27.0 |
| Cisco | Cisco | Open Source Snort3 3.1.28.0 |
| Cisco | Cisco | Open Source Snort3 3.1.29.0 |
| Cisco | Cisco | Open Source Snort3 3.1.30.0 |
| Cisco | Cisco | Open Source Snort3 3.1.31.0 |
| Cisco | Cisco | Open Source Snort3 3.1.32.0 |
| Cisco | Cisco | Open Source Snort3 3.1.36.0 |
| Cisco | Cisco | Open Source Snort3 3.1.38.0 |
| Cisco | Cisco | Open Source Snort3 3.1.39.0 |
| Cisco | Cisco | Open Source Snort3 3.1.40.0 |
| Cisco | Cisco | Open Source Snort3 3.1.41.0 |
| Cisco | Cisco | Open Source Snort3 3.1.42.0 |
| Cisco | Cisco | Open Source Snort3 3.1.43.0 |
| Cisco | Cisco | Open Source Snort3 3.1.45.0 |
| Cisco | Cisco | Open Source Snort3 3.1.47.0 |
| Cisco | Cisco | Open Source Snort3 3.1.48.0 |
| Cisco | Cisco | Open Source Snort3 3.1.50.0 |
| Cisco | Cisco | Open Source Snort3 3.1.51.0 |
| Cisco | Cisco | Open Source Snort3 3.1.52.0 |
| Cisco | Cisco | Open Source Snort3 3.1.53.0 |
| Cisco | Cisco | Open Source Snort3 3.1.55.0 |
| Cisco | Cisco | Open Source Snort3 3.1.56.0 |
| Cisco | Cisco | Open Source Snort3 3.1.57.0 |
| Cisco | Cisco | Open Source Snort3 3.1.58.0 |
| Cisco | Cisco | Open Source Snort3 3.1.59.0 |
| Cisco | Cisco | Open Source Snort3 3.1.60.0 |
| Cisco | Cisco | Open Source Snort3 3.1.61.0 |
| Cisco | Cisco | Open Source Snort3 3.1.62.0 |
| Cisco | Cisco | Open Source Snort3 3.1.63.0 |
| Cisco | Cisco | Open Source Snort3 3.1.64.0 |
| Cisco | Cisco | Open Source Snort3 3.1.65.0 |
| Cisco | Cisco | Open Source Snort3 3.1.66.0 |
| Cisco | Cisco | Open Source Snort3 3.1.67.0 |
| Cisco | Cisco | Open Source Snort3 3.1.69.0 |
| Cisco | Cisco | Open Source Snort3 3.1.70.0 |
| Cisco | Cisco | Open Source Snort3 3.1.71.0 |
| Cisco | Cisco | Open Source Snort3 3.1.72.0 |
| Cisco | Cisco | Open Source Snort3 3.1.73.0 |
| Cisco | Cisco | Open Source Snort3 3.1.74.0 |
| Cisco | Cisco | Open Source Snort3 3.1.75.0 |
| Cisco | Cisco | Open Source Snort3 3.1.76.0 |
| Cisco | Cisco | Open Source Snort3 3.1.77.0 |
| Cisco | Cisco | Open Source Snort3 3.1.78.0 |
| Cisco | Cisco | Open Source Snort3 3.1.81.0 |
| Cisco | Cisco | Open Source Snort3 3.1.82.0 |
| Cisco | Cisco | Open Source Snort3 3.1.83.0 |
| Cisco | Cisco | Open Source Snort3 3.1.84.0 |
| Cisco | Cisco | Open Source Snort3 3.2.1.0 |
| Cisco | Cisco | Open Source Snort3 3.2.2.0 |
| Cisco | Cisco | Open Source Snort3 3.3.0.0 |
| Cisco | Cisco | Open Source Snort3 3.3.1.0 |
| Cisco | Cisco | Open Source Snort3 3.3.2.0 |
| Cisco | Cisco | Open Source Snort3 3.3.3.0 |
| Cisco | Cisco | Open Source Snort3 3.3.4.0 |
| Cisco | Cisco | Open Source Snort3 3.3.5.0 |
| Cisco | Cisco | Open Source Snort3 3.3.7.0 |
| Cisco | Cisco | Open Source Snort3 3.5.0.0 |
| Cisco | Cisco | Open Source Snort3 3.5.1.0 |
| Cisco | Cisco | Open Source Snort3 3.8.1.0 |
| Cisco | Cisco | Open Source Snort3 3.6.0.0 |
| Cisco | Cisco | Open Source Snort3 3.6.2.0 |
| Cisco | Cisco | Open Source Snort3 3.9.3.0 |
| Cisco | Cisco | Open Source Snort3 3.7.2.0 |
| Cisco | Cisco | Open Source Snort3 3.7.0.0 |
| Cisco | Cisco | Open Source Snort3 3.9.6.0 |
| Cisco | Cisco | Open Source Snort3 3.10.0.0 |
| Cisco | Cisco | Open Source Snort3 3.10.2.0 |
| Cisco | Cisco | Open Source Snort3 3.7.4.0 |
| Cisco | Cisco | Open Source Snort3 3.9.0.0 |
| Cisco | Cisco | Open Source Snort3 3.5.2.0 |
| Cisco | Cisco | Open Source Snort3 3.12.1.0 |
| Cisco | Cisco | Open Source Snort3 3.6.1.0 |
| Cisco | Cisco | Open Source Snort3 3.9.2.0 |
| Cisco | Cisco | Open Source Snort3 3.6.3.0 |
| Cisco | Cisco | Open Source Snort3 3.9.5.0 |
| Cisco | Cisco | Open Source Snort3 3.7.1.0 |
| Cisco | Cisco | Open Source Snort3 3.9.7.0 |
| Cisco | Cisco | Open Source Snort3 3.7.3.0 |
| Cisco | Cisco | Open Source Snort3 3.10.1.0 |
| Cisco | Cisco | Open Source Snort3 3.9.1.0 |
| Cisco | Cisco | Open Source Snort3 3.11.1.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.0.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.1.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.2.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.0.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.5 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.3.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.3.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.6 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.5 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.4.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.3.1.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.6.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.5.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.6 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.6.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.1.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.7 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.5.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.3.1.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.8 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.8.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.6.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.9 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.7 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.7.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.10 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.8 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.7.10 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.7.11 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.8.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.2.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.7.10.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.10.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 10.0.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.9 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.11 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.7 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.2 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.13.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.3 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.14.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.4 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.3a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.16.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.4a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.2c |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.4b |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.2a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.17.1 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.3a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.3 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5b |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5c |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.4 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.1 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.6 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.4c |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5d |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.2 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 26.1.1 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.5 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.5a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.7 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.7a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.7b |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.3a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.8 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.6 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.4 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 26.1.2 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-128 | Wrap around errors occur whenever a value is incremented past the maximum value for its type and therefore "wraps around" to a very small, negative, or undefined value. |
