Cisco Snort NetFlow Detection Engine denial of service

Summaryinfo

A vulnerability described as critical has been identified in Cisco Snort. This impacts an unknown function of the component NetFlow Detection Engine. The manipulation results in denial of service. This vulnerability is cataloged as CVE-2026-20019. The attack may be launched remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as critical, was found in Cisco Snort (unknown version). Affected is an unknown code block of the component NetFlow Detection Engine. The manipulation with an unknown input leads to a denial of service vulnerability. CWE is classifying the issue as CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. This is going to have an impact on availability. CVE summarizes:

Multiple Cisco products are affected by a vulnerability in the Snort 3 NetFlow 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 UDP Netflow Protocol packets. An attacker could exploit this vulnerability by sending a single crafted Netflow packet through an established connection to be parsed by Snort 3. A successful exploit could allow the attacker to cause the Snort 3 Detection Engine to restart unexpectedly, resulting in a DoS condition.

The advisory is shared for download at sec.cloudapps.cisco.com. This vulnerability is traded as CVE-2026-20019 since 10/08/2025. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/21/2026). The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading eliminates this vulnerability.

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Productinfo

Vendor

• Cisco

Name

• Snort

License

• commercial

Website

• Vendor: https://www.cisco.com/

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