CVE-2026-20105
Cisco Adaptive Security Appliance Software 9.12.1 – 9.16.4.85
Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:HSummary
CVE-2026-20105 is a high-severity Missing Release of Memory after Effective Lifetime (CWE-401) vulnerability in Cisco Adaptive Security Appliance Software. Its CVSS base score is 7.7 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 24th 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-2026-20105 is a memory exhaustion vulnerability in the Remote Access SSL VPN functionality of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software. The issue arises from the software trusting user input without proper validation, which could allow an authenticated, remote attacker with a valid VPN connection to exhaust device memory. This vulnerability does not affect the management or MUS interfaces and is rated with a CVSS v3.1 base score of 7.7 (AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H), associated with CWE-401 (Memory Buffer of Resource Management Errors).
An attacker must possess a valid, authenticated Remote Access SSL VPN connection to exploit this vulnerability. By sending crafted packets to the VPN server, the attacker can trigger memory exhaustion on the device, leading to a reload and a denial-of-service (DoS) condition that disrupts VPN services.
Cisco has published a security advisory at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-m9sx6MbC providing details on the vulnerability, affected versions, and recommended mitigation steps, including software updates.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9442
Vulnerability Data
A vulnerability in the Remote Access SSL VPN functionality of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker with a valid VPN connection to exhaust device memory…
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resulting in a denial of service (DoS) condition.This does not affect the management or MUS interfaces. This vulnerability is due to trusting user input without validation. An attacker could exploit this vulnerability by sending crafted packets to the Remote Access SSL VPN server. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.
- 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 (static analysis, fuzzing, or runtime leak detection) directly finds missing deallocation.
Requiring documented development standards and tools can mandate memory-management disciplines that avoid leaks at introduction.
Engineering principles applied during development can require explicit resource-release patterns that stop memory leaks from being coded.
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.
Secure SDLC practices directly enforce proper memory allocation/deallocation via coding standards, reviews, and tooling.
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.
Security testing in development can detect unreleased memory, providing partial coverage of the weakness.
Secure development life cycle mandates memory-management practices that reduce missing-release defects.
Application security requirements can specify explicit memory-release rules, partially mitigating the weakness.
Secure system architecture and engineering principles include resource-management guidelines that address memory leaks.
Secure coding standards directly require proper allocation/deallocation, covering most of this weakness.
Capacity management may detect memory exhaustion symptoms but does not prevent the coding flaw.