Cisco ASA TCP SYN Flood DoS via Mismanaged Connection Limits
CVE-2026-20082 Published on March 4, 2026

A vulnerability in the handling of the embryonic connection limits in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause incoming TCP SYN packets to be dropped incorrectly. This vulnerability is due to improper handling of new, incoming TCP connections that are destined to management or data interfaces when the device is under a TCP SYN flood attack. An attacker could exploit this vulnerability by sending a crafted stream of traffic to an affected device. A successful exploit could allow the attacker to prevent all incoming TCP connections to the device from being established, including remote management access, Remote Access VPN (RAVPN) connections, and all network protocols that are TCP-based. This results in a denial of service (DoS) condition for affected features.

NVD

Vulnerability Analysis

CVE-2026-20082 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
NONE
User Interaction:
NONE
Scope:
CHANGED
Confidentiality Impact:
NONE
Integrity Impact:
NONE
Availability Impact:
HIGH

Weakness Type

Missing Release of Resource after Effective Lifetime

The software does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed. When a resource is not released after use, it can allow attackers to cause a denial of service by causing the allocation of resources without triggering their release. Frequently-affected resources include memory, CPU, disk space, power or battery, etc.


Products Associated with CVE-2026-20082

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Cisco Adaptive Security Appliance
 

Affected Versions

Cisco Secure Firewall Adaptive Security Appliance (ASA) Software Version 9.20.4.14 is affected by CVE-2026-20082

Exploit Probability

EPSS
0.11%
Percentile
28.79%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.