CVE-2026-20082
Cisco Adaptive Security Appliance Software 9.20.4.14 – 9.20.4.19
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:HSummary
CVE-2026-20082 is a high-severity Missing Release of Resource after Effective Lifetime (CWE-772) vulnerability in Cisco Adaptive Security Appliance Software. Its CVSS base score is 8.6 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 34th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-20082 is a vulnerability in the handling of embryonic connection limits in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software. The issue causes incoming TCP SYN packets to be dropped incorrectly due to improper processing of new TCP connections destined for management or data interfaces during a TCP SYN flood attack.
An unauthenticated, remote attacker can exploit this vulnerability by sending a crafted stream of traffic to an affected device. Successful exploitation prevents all incoming TCP connections from being established, including remote management access, Remote Access VPN (RAVPN) connections, and TCP-based network protocols, resulting in a denial-of-service (DoS) condition. The vulnerability has a CVSS v3.1 base score of 8.6 (AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H) and is associated with CWE-772.
The Cisco Security Advisory provides details on mitigation and patch information at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-dos-FCvLD6vR.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9471
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover missing resource releases through dynamic analysis or stress testing.
Requiring documented development standards and tools can mandate explicit resource-release patterns in code.
Resource-quota allocation limits the blast radius of an unreleased-resource exhaustion condition.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Lifecycle management explicitly requires handling resources through end-of-life including release.
Secure SDLC practices directly prevent missing resource-release defects during development.
Runtime monitoring may surface resource-exhaustion symptoms but does not address release logic.
Capacity monitoring can detect exhaustion caused by unreleased resources but does not prevent the root defect.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Explicit information-deletion requirements directly address timely release of resources after use.
Secure-SDLC practices include resource-management reviews, yet the control covers the entire lifecycle, not just this weakness.
Secure-coding rules can mandate explicit resource-release patterns, but the control is broader than this single weakness.
Change-management processes may catch missing de-allocation during reviews, but the control itself does not target resource lifetime.
Configuration baselines can enforce resource limits or timeouts, indirectly reducing exposure to leaks.