CVE-2021-40116 Multiple Cisco Products Snort Rule Denial of Service Vulnerability
Remote attackers can cause denial of service on Cisco Firepower devices by sending crafted packets if specific Snort3 rules are configured.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2021-40116?
CVE-2021-40116 is a high-severity denial of service vulnerability in Cisco Secure Firewall Management Center, published on 27 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Multiple Cisco products are affected by a vulnerability in Snort rules that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.The vulnerability is due to improper handling of the Block with Reset or Interactive Block with Reset actions if a rule is configured without proper constraints. An attacker could exploit this vulnerability by sending a crafted IP packet to the affected device. A successful exploit could allow the attacker to cause through traffic to be dropped. Note: Only products with Snort3 configured and either a rule with Block with Reset or Interactive Block with Reset actions configured are vulnerable. Products configured with Snort2 are not vulnerable.
Weakness: CWE-241
Which versions are affected by CVE-2021-40116?
It affects 3 products.
Products include Cisco Secure Firewall Management Center, Cisco Secure Firewall Threat Defense, Cisco Snort.
How do I fix CVE-2021-40116?
No fix has been published for CVE-2021-40116 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2021-40116 being exploited?
There is no known exploitation of CVE-2021-40116 in the wild and no public exploit code.
Other vulnerabilities in Cisco Secure Firewall Management Center
- CVE-2026-20079 Cisco Firewall Management Center Authentication Bypass Using an Alternate Path or Channel
- CVE-2026-20131 Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data
- CVE-2026-20316 Cisco Secure Firewall Management Center Use of Hard-coded Password
- CVE-2025-20265 Cisco Secure Firewall Management Center Software Radius Remote Code Execution Vulnerability
- CVE-2024-20424 Command injection in Cisco Firepower Management Center
Sources
Also known as GHSA-w5gp-j3p5-92ch.