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Multiple Cisco products incorporating the Snort 3 detection engine are affected by a vulnerability in the Visual Basic for Applications (VBA) decompression feature. The flaw stems from improper error checking during the decompression of VBA data. Specifically, when the Snort 3 Detection Engine processes VBA data, inadequate validation of decompression routines allows malformed input to trigger an unhandled exception. This issue is categorized under CWE-786: Access of Memory Location Before Start of Buffer.
An unauthenticated, remote attacker can exploit this vulnerability by sending crafted VBA data packets to the Snort 3 Detection Engine on a targeted Cisco device. The attack requires no authentication and can be executed over the network without user interaction. Upon receiving the malicious VBA data, the detection engine attempts to decompress it; however, due to the lack of proper error checking, the process enters an unexpected state and crashes. This causes the Snort 3 Detection Engine to unexpectedly restart, resulting in a denial-of-service (DoS) condition.
The CVSS v3.1 base score is 5.8 (MEDIUM) with the vector: AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L. The attack complexity is low, requires no privileges, and no user interaction, with a scope change and low availability impact. The vulnerability affects multiple Cisco products that run Snort 3, including Cisco Secure Firewall Threat Defense Software, Cisco ASA Software, and Cisco IOS XE. According to available data, Snort versions from 3.0.0-233 up to (but not including) 3.9.6.0 are affected. Cisco has released security updates addressing this issue through multiple bug IDs including CSCwq23369, CSCwq23372, CSCwq23373, CSCwq23377, CSCwq97494, CSCwq97497, CSCwq97658, CSCwq97660, CSCwq97748, CSCwq97750, and CSCwr21406.
DailyCVE Form:
Platform: Cisco Snort 3
Version: 3.0.0-233 to 3.9.6.0
Vulnerability: Improper VBA decompression
Severity: 5.8 MEDIUM
date: 03/04/2026
Prediction: 03/04/2026 (Patch Released)
What Undercode Say:
Check Snort 3 version on Cisco device show version | include Snort show running-config | include snort Verify Snort 3 process status show processes | include snort show service-policy | include Snort Check for Snort 3 crash logs show logging | include Snort | include crash show logging | include VBA | include error Identify affected Snort 3 package version (Alpine Linux example) apk info snort snort -V Nessus plugin ID for vulnerability scanning Plugin: 311459 - Multiple Cisco Products Snort 3 VBA Decompression DoS https://www.tenable.com/plugins/nessus/311459
Exploit: (Educational Purposes!)
The exploitation process involves crafting malicious VBA data that triggers improper error handling during decompression:
1. Identify a target Cisco device running Snort 3 Detection Engine with an affected version (3.0.0-233 to <3.9.6.0).
2. Craft a network packet containing malformed VBA data designed to cause a decompression error.
3. Transmit the crafted packet to the Snort 3 Detection Engine on the target device.
4. The detection engine processes the VBA data, encounters the malformed input, and due to insufficient error checking, crashes and restarts.
5. Successful exploitation results in a DoS condition where the Snort 3 Detection Engine unexpectedly restarts, interrupting network traffic inspection.
The attack vector is remote, requires no authentication, and can be executed with low complexity.
Protection:
– Upgrade Snort 3 to version 3.9.6.0 or later, which contains the fix for this vulnerability.
– Apply vendor-supplied security updates from Cisco referenced in bug IDs CSCwq23369, CSCwq23372, CSCwq23373, CSCwq23377, CSCwq97494, CSCwq97497, CSCwq97658, CSCwq97660, CSCwq97748, CSCwq97750, and CSCwr21406.
– Implement network segmentation and access control measures to limit exposure of vulnerable Snort 3 instances to untrusted networks.
– Deploy monitoring solutions that can detect and alert on unusual restart patterns of security appliances.
– Regularly conduct security assessments and vulnerability scanning using Nessus plugin ID 311459 to identify vulnerable systems.
Impact:
Successful exploitation causes the Snort 3 Detection Engine to crash and unexpectedly restart, creating a denial-of-service condition. This disruption temporarily removes network visibility for intrusion detection and prevention, potentially allowing malicious traffic to go undetected during the engine recovery period. The vulnerability is particularly concerning due to its remote, unauthenticated attack vector, making it accessible to any actor capable of sending packets to the targeted device. Organizations should prioritize mitigation as the flaw affects multiple Cisco product lines including Secure Firewall Threat Defense, ASA, and IOS XE platforms.
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Sources:
Reported By: nvd.nist.gov
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