CVE-2021-40116 Vulnerability Analysis & Exploit Details

CVE-2021-40116
Vulnerability Scoring

8.6

/10

Severe Risk

Cybersecurity professionals consider CVE-2021-40116 an immediate threat requiring urgent mitigation.

Attack Complexity Details

Attack Complexity: Low
Exploits can be performed without significant complexity or special conditions.
Attack Vector: Network
Vulnerability is exploitable over a network without physical access.
Privileges Required: None
No privileges are required for exploitation.
Scope: Changed
Successful exploitation can impact components beyond the vulnerable component.
User Interaction: None
No user interaction is necessary for exploitation.

CVE-2021-40116 Details

Status: Modified

Last updated: 🕧 07 Jul 2025, 12:40 UTC
Originally published on: 🕖 27 Oct 2021, 19:15 UTC

Time between publication and last update: 1348 days

CVSS Release: version 3

CVSS3 Source

psirt@cisco.com

CVSS3 Type

Secondary

CVSS3 Vector

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

CVE-2021-40116 Vulnerability Summary

CVE-2021-40116: 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.

Assessing the Risk of CVE-2021-40116

Access Complexity Graph

The exploitability of CVE-2021-40116 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2021-40116

With low attack complexity and no required privileges, CVE-2021-40116 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2021-40116, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2021-40116, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

Confidentiality: None
CVE-2021-40116 has no significant impact on data confidentiality.
Integrity: None
CVE-2021-40116 poses no threat to data integrity.
Availability: High
CVE-2021-40116 can disrupt system operations, potentially causing complete denial of service (DoS).

Exploit Prediction Scoring System (EPSS)

The EPSS score estimates the probability that this vulnerability will be exploited in the near future.

EPSS Score: 0.159% (probability of exploit)

EPSS Percentile: 53.82% (lower percentile = lower relative risk)
This vulnerability is less risky than approximately 46.18% of others.

CVE-2021-40116 References

External References

CWE Common Weakness Enumeration

NVD-CWE-noinfo

Vulnerable Configurations

cpe:2.3:a:cisco:firepower_threat_defense:6.4.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.6:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.6:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.7:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.7:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.8:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.8:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.9:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.9:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.10:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.10:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.11:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.11:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.12:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.4.0.12:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.6.5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.7.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.7.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.7.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.7.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.7.0.2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:6.7.0.2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:7.0.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:7.0.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:7.0.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:7.0.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:secure_firewall_management_center:3.1.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:secure_firewall_management_center:3.1.0.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-233:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-233:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-239:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-239:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-240:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-240:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-241:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-241:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-242:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-242:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-243:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-243:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-244:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-244:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-245:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-245:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-246:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-246:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-247:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-247:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-248:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-248:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-249:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-249:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-250:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-250:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-251:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-251:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-252:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-252:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-253:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-253:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-254:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-254:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-255:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-255:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-256:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-256:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-257:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-257:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-258:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-258:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-259:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-259:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-260:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-260:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-261:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-261:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-262:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-262:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-263:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-263:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-264:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-264:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-265:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-265:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-266:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-266:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-267:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-267:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-268:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-268:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-269:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-269:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-270:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.0-270:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.1-5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-6:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.2-6:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-6:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.0.3-6:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.1.0.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:snort:3.1.0.0:*:*:*:*:*:*:*

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