CVE-2026-20082
TCP SYN Flood Handling Flaw in Cisco ASA Causes DoS
Publication date: 2026-03-04
Last updated on: 2026-05-04
Assigner: Cisco Systems, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| cisco | adaptive_security_appliance_software | From 9.20.4.14 (inc) to 9.20.4.19 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-772 | The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
CVE-2026-20082 is a high-severity vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software version 9.20.4.14. It occurs due to improper handling of embryonic TCP connection limits during TCP SYN flood attacks.
An unauthenticated remote attacker can exploit this vulnerability by sending a crafted stream of TCP SYN packets to the device. This causes the device to incorrectly drop incoming TCP SYN packets destined for management or data interfaces.
As a result, the device prevents all incoming TCP connections from being established, including remote management access, Remote Access VPN (RAVPN) connections, and all TCP-based network protocols, leading to a denial of service (DoS) condition.
How can this vulnerability impact me? :
This vulnerability can cause a denial of service (DoS) condition on affected Cisco Secure Firewall ASA devices.
An attacker exploiting this issue can prevent all incoming TCP connections, which includes blocking remote management access and Remote Access VPN (RAVPN) connections.
This disruption affects critical device functionality and network operations, potentially causing significant operational impact.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
There is no specific information provided about detection methods or commands to identify this vulnerability on your network or system.
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, Cisco recommends upgrading to the fixed software release 9.20.4.19 of Cisco Secure Firewall ASA Software.
There are no workarounds available for this vulnerability, so applying the software update is the primary mitigation step.
Ensure device compatibility and sufficient memory before upgrading, and contact Cisco TAC for assistance if needed.