Medium severity · published Oct 21, 2026
CVE-2026-20218
Cisco Secure Firewall Threat Defense Snort 3 Visual Basic for Applications Buffer Overflow Denial of Service Vulnerability
New
5.8
CVSS
0.6%
EPSS
No
On KEV
Description
A vulnerability in the Snort 3 Visual Basic for Applications (VBA) Decompression Engine of multiple Cisco products could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart unexpectedly, resulting in a denial of service (DoS) condition.   This vulnerability is due to improper range checking when Snort 3 decompresses VBA data, which is user controlled. An attacker could exploit this vulnerability by sending crafted VBA data to the Snort 3 Detection Engine of a targeted device. A successful exploit could allow the attacker to cause an overflow of stack data, which could result in a DoS condition.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 50% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CO
Cisco Open Source Snort3 · Cisco
3.12.2.0; 3.1.2.0; 3.1.3.0; 3.1.4.0; 3.1.5.0; 3.1.6.0; +34 more · source: vendor
CS
Cisco Secure Firewall Threat Defense (FTD) Software · Cisco
7.2.0; 7.2.0.1; 7.2.1; 7.3.0; 7.2.2; 7.2.3; +34 more · source: vendor
CU
Cisco UTD SNORT IPS Engine Software · Cisco
17.12.1a; 17.12.2; 17.13.1a; 17.12.3; 17.14.1a; 17.12.4; +32 more · source: vendor
In the news
VulnerabilityHigh
ZDI-26-788: Cisco Snort OLE VBA Decompression Stack-based Buffer Overflow Remote Code Execution Vulnerability
This vulnerability allows remote attackers to execute arbitrary code on affected installations of Cisco Snort. Authentication is not required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 8.1. The following CVEs are assigned: CVE-2026-20218.
Oct 22, 2026·Zero Day Initiative
Affected product
CO
Cisco Open Source Snort3
Cisco
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