Cyber Resilience

CVE-2023-20042

Cisco Adaptive Security Appliance Software 9.16.1 … 9.19.1

Published
01 November 2023
Modified
11 August 2026
Patch / advisory
View advisory
CVSS Score v3.1 6.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
EPSS Score 0.0067 49th percentile
Risk Priority 51 floored blend · peak EPSS

Summary

CVE-2023-20042 is a medium-severity Improper Resource Shutdown or Release (CWE-404) vulnerability in Cisco Adaptive Security Appliance Software. Its CVSS base score is 6.8 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 49th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability Data

A vulnerability in the AnyConnect SSL VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.…

more

This vulnerability is due to an implementation error within the SSL/TLS session handling process that can prevent the release of a session handler under specific conditions. An attacker could exploit this vulnerability by sending crafted SSL/TLS traffic to an affected device, increasing the probability of session handler leaks. A successful exploit could allow the attacker to eventually deplete the available session handler pool, preventing new sessions from being established and causing a DoS condition.

CWE(s)
CWE-404NVD-CWE-noinfo

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
T1499.001 OS Exhaustion Flood Impact
Adversaries may launch a denial of service (DoS) attack targeting an endpoint's operating system (OS).
attack.mitre.org →
T1499.003 Application Exhaustion Flood Impact
Adversaries may target resource intensive features of applications to cause a denial of service (DoS), denying availability to those applications.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-20050Same product: Cisco Secure Firewall Threat Defense
CVE-2018-0101Same product: Cisco Adaptive Security Appliance Software
CVE-2025-20127Same product: Cisco Adaptive Security Appliance Software
CVE-2026-20014Same product: Cisco Adaptive Security Appliance Software
CVE-2026-20021Same product: Cisco Adaptive Security Appliance Software
CVE-2026-20013Same product: Cisco Adaptive Security Appliance Software
CVE-2026-20106Same product: Cisco Adaptive Security Appliance Software
CVE-2026-20015Same product: Cisco Adaptive Security Appliance Software
CVE-2026-20105Same product: Cisco Adaptive Security Appliance Software
CVE-2026-20103Same product: Cisco Adaptive Security Appliance Software

Affected Assets

cisco
secure firewall threat defense
7.0.0, 7.0.0.1, 7.0.1, 7.0.1.1, 7.0.2
cisco
adaptive security appliance software
9.16.1, 9.16.1.28, 9.16.2, 9.16.2.11, 9.16.2.13

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

CP-5 Contingency Plan Update
addresses: CWE-404

Contingency plan updates incorporate proper resource shutdown and release steps, preventing attackers from leveraging incomplete cleanup during recovery scenarios.

SC-10 Network Disconnect
addresses: CWE-404

Mandates explicit shutdown of the network connection at session conclusion, directly addressing improper resource release.

SC-4 Information in Shared System Resources
addresses: CWE-404

Requires proper shutdown/release procedures that include overwriting or isolating data to block unintended transfer via reused system objects.

SI-17 Fail-safe Procedures
addresses: CWE-404

Procedures can mandate orderly shutdown or release of resources when failures occur, preventing improper resource handling after a fault.

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.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly include coding standards for correct resource allocation and release.

DE.CM-09 partial match
prevents

Runtime monitoring can detect resource exhaustion caused by improper shutdown or release.

ID.AM-08 partial match
prevents

Lifecycle management of assets can encompass proper resource release at end-of-life or shutdown.

PR.IR-04 partial match
prevents

Capacity management helps surface leaks from unreleased resources but does not prevent the coding flaw.

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.

A.5.37 Documented operating procedures partial match
prevents

Including restart, recovery and media-handling instructions reduces the likelihood that resources or sensitive data will be left in an exposed or improperly released state after a failure.

References