Is CVE-2021-40116 in the CISA KEV catalog?

No. CVE-2021-40116 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-40116?

CVE-2021-40116 has a CVSS v3 base score of 8.6 (HIGH).

What is the EPSS score for CVE-2021-40116?

CVE-2021-40116 has an EPSS score of 1.35% (68th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-40116?

Upgrade firepower threat defense to 7.0.1 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2021-40116

HIGH

8.6

CVSS v3

NVD

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.

CWE-241

How to fix

Remediation Available

firepower threat defenseNVD

Affected:>= 7.0.0, < 7.0.1Fixed in:7.0.1CVE-2021-40116derived from NVD

snortNVD

Affected:>= 3.0.0.0, < 3.1.0.100Fixed in:3.1.0.100CVE-2021-40116derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeChanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Exploit Intelligence

1.35%probability of exploitation in 30 days

68thpercentile

Moderate risk: more likely to be exploited than 68% of all known CVEs.

References

Vendor Advisory1

tools.cisco.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-07-07.