Detections
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Multiple Cisco Products Snort 3 Generic Routing Encapsulation DoS (cisco-sa-snort3-gre-JNpMHrTv)

medium Nessus Plugin ID 370005

Synopsis

The remote device is missing a vendor-supplied security patch

Description

According to its self-reported version, Cisco ASA Software is affected by a vulnerability.

 - 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. (CVE-2026-20221)

Please see the included Cisco BIDs and Cisco Security Advisory for more information.

Solution

Upgrade to the relevant fixed version referenced in Cisco bug IDs CSCwt66239, CSCwt83029, CSCwt83034, CSCwu04383

See Also

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwt66239

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwt83029

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwt83034

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwu04383

http://www.nessus.org/u?bcf1e449

Plugin Details

Severity: Medium

ID: 370005

File Name: cisco-sa-snort3-gre-JNpMHrTv-asa.nasl

Version: 1.1

Type: Local

Family: CISCO

Published: 10/21/2026

Updated: 10/21/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 1.2

Percentile: 0.01

CVSS v2

Risk Factor: Medium

Base Score: 5

Temporal Score: 3.7

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:P

CVSS Score Source: CVE-2026-20221

CVSS v3

Risk Factor: Medium

Base Score: 5.8

Temporal Score: 5.1

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:cisco:adaptive_security_appliance_software

Required KB Items: Host/Cisco/ASA/model

Exploit Ease: No known exploits are available

Patch Publication Date: 10/21/2026

Vulnerability Publication Date: 10/21/2026

Reference Information

CVE: CVE-2026-20221