Stack-based buffer overflow in Snort - CVE-2026-20218
Published: October 21, 2026
Vulnerability identifier: #VU156724
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-20218
CWE-ID: CWE-121
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service by triggering an unexpected restart of the Snort 3 Detection Engine.
The vulnerability exists due to a stack-based buffer overflow caused by improper range checking in the Snort 3 Visual Basic for Applications (VBA) Decompression Engine when decompressing user-controlled VBA data. A remote attacker can send specially crafted VBA data to the Snort 3 Detection Engine of a targeted device to overflow stack data and cause a denial of service.
Cisco Secure Firewall Threat Defense deployments are affected only when Snort 3 is configured and at least one Snort 3 Detector is configured for VBA macro decompression.
Affected software
Snort
How to mitigate CVE-2026-20218
Install security update from vendor's website.
Snort - update to 3.12.4.0