CVE-2026-20221
Description
Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine. This vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required.
How to fix
Sources list no fixed version or patch link for this vulnerability.
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Cisco Cisco Cyber Vision | 3.0.0, 3.0.2, 3.0.3, 3.0.1, 3.1.0, 3.0.4, 3.1.1, 3.1.2, 3.2.0, 3.0.5, 3.2.1, 3.0.6, 3.2.2, 3.2.3, 3.2.4, 4.0.0, 4.0.1, 4.0.2, 4.0.3, 4.1.0, 4.1.1, 4.1.2, 4.1.3, 4.1.4, 4.2.0, 4.2.1, 4.1.5, 4.2.2, 4.2.X, 4.2.3, 4.2.4, 4.2.6, 4.1.6, 4.3.0, 4.3.1, 4.3.2, 4.3.3, 4.4.0, 4.4.1, 4.4.2, 4.4.3, 4.1.7, 5.0.0, 5.0.1, 5.0.2, 5.1.0, 5.1.1, 5.1.2, 5.1.3, 5.2.0, 5.2.1, 5.3.0, 5.3.1, 5.3.2, 5.3.3, 5.5.1, 5.6.1, 5.6.0, 5.4.0, 5.4.1, 5.4.2 | — |
| Cisco Cisco Open Source Snort3 | 3.12.2.0, 3.1.2.0, 3.1.3.0, 3.1.4.0, 3.1.5.0, 3.1.6.0, 3.1.7.0, 3.1.8.0, 3.1.9.0, 3.1.10.0, 3.1.12.0, 3.1.13.0, 3.1.14.0, 3.1.15.0, 3.1.16.0, 3.1.17.0, 3.1.18.0, 3.1.19.0, 3.1.20.0, 3.1.21.0, 3.1.22.0, 3.1.23.0, 3.1.24.0, 3.1.25.0, 3.1.27.0, 3.1.28.0, 3.1.29.0, 3.1.30.0, 3.1.31.0, 3.1.32.0, 3.1.36.0, 3.1.38.0, 3.1.39.0, 3.1.40.0, 3.1.41.0, 3.1.42.0, 3.1.43.0, 3.1.45.0, 3.1.47.0, 3.1.48.0, 3.1.50.0, 3.1.51.0, 3.1.52.0, 3.1.53.0, 3.1.55.0, 3.1.56.0, 3.1.57.0, 3.1.58.0, 3.1.59.0, 3.1.60.0, 3.1.61.0, 3.1.62.0, 3.1.63.0, 3.1.64.0, 3.1.65.0, 3.1.66.0, 3.1.67.0, 3.1.69.0, 3.1.70.0, 3.1.71.0, 3.1.72.0, 3.1.73.0, 3.1.74.0, 3.1.75.0, 3.1.76.0, 3.1.77.0, 3.1.78.0, 3.1.81.0, 3.1.82.0, 3.1.83.0, 3.1.84.0, 3.2.1.0, 3.2.2.0, 3.3.0.0, 3.3.1.0, 3.3.2.0, 3.3.3.0, 3.3.4.0, 3.3.5.0, 3.3.7.0, 3.5.0.0, 3.5.1.0, 3.8.1.0, 3.6.0.0, 3.6.2.0, 3.9.3.0, 3.7.2.0, 3.7.0.0, 3.9.6.0, 3.10.0.0, 3.10.2.0, 3.7.4.0, 3.9.0.0, 3.5.2.0, 3.12.1.0, 3.6.1.0, 3.9.2.0, 3.6.3.0, 3.9.5.0, 3.7.1.0, 3.9.7.0, 3.7.3.0, 3.10.1.0, 3.9.1.0, 3.11.1.0 | — |
| Cisco Cisco Secure Firewall Threat Defense (FTD) Software | 7.0.0, 7.0.0.1, 7.0.1, 7.0.1.1, 7.0.2, 7.2.0, 7.0.2.1, 7.0.3, 7.2.0.1, 7.0.4, 7.2.1, 7.0.5, 7.3.0, 7.2.2, 7.2.3, 7.3.1, 7.2.4, 7.0.6, 7.2.5, 7.2.4.1, 7.3.1.1, 7.4.0, 7.0.6.1, 7.2.5.1, 7.4.1, 7.2.6, 7.0.6.2, 7.4.1.1, 7.2.7, 7.2.5.2, 7.3.1.2, 7.2.8, 7.6.0, 7.4.2 | — |
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