Cisco Snort 3 SMTP MIME Decoder input validation

Summaryinfo

A vulnerability marked as critical has been reported in Cisco Snort 3. This affects an unknown function of the component SMTP MIME Decoder. The manipulation leads to input validation. This vulnerability is listed as CVE-2026-20011. The attack may be initiated remotely. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Cisco Snort 3 (the affected version is unknown). This issue affects an unknown code of the component SMTP MIME Decoder. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is availability. The summary by CVE is:

Multiple Cisco products are affected by a vulnerability in the Snort 3 SMTP MIME Decoder that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart. This vulnerability is due to a lack of error checking when the MIME fields of the SMTP header are parsed. An attacker could exploit this vulnerability by sending crafted SMTP packets through an established connection to be parsed by Snort 3. A successful exploit could allow the attacker to cause a denial of service (DoS) condition when the Snort 3 Detection Engine unexpectedly restarts.

It is possible to read the advisory at sec.cloudapps.cisco.com. The identification of this vulnerability is CVE-2026-20011 since 10/08/2025. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/21/2026).

Upgrading eliminates this vulnerability.

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Productinfo

Vendor

• Cisco

Name

• Snort 3

License

• commercial

Website

• Vendor: https://www.cisco.com/

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