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.
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.
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
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| Cisco | Cisco Cyber Vision | unknown |
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| Cisco | Cisco Open Source Snort3 | unknown |
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| Cisco | Cisco Secure Firewall Threat Defense (FTD) Software | unknown |
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| Cisco | Cisco Umbrella Insights Virtual Appliance | unknown |
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| Cisco | Cisco UTD SNORT IPS Engine Software | unknown |
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No data available yet.
Remediation
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
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Advisories
No advisories yet.
References
History
Wed, 21 Oct 2026 17:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities | |
| Weaknesses | CWE-476 | |
| References |
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| Metrics |
cvssV3_1
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Subscriptions
No data.
MITRE
Status: PUBLISHED
Assigner: cisco
Published:
Updated: 2026-10-21T16:12:53.435Z
Reserved: 2025-10-08T11:59:15.398Z
Link: CVE-2026-20221
Vulnrichment
No data.
NVD
Status : Awaiting Analysis
Published: 2026-10-21T17:18:27.947
Modified: 2026-10-21T18:54:37.403
Link: CVE-2026-20221
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
-
CWE-476
NULL Pointer Dereference