Cisco Secure Firewall Adaptive Security…: Missing Release of Memory after Effective Lifetime
CVE-2026-20105 is a high-severity missing release of memory after effective lifetime vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software from Cisco, with a CVSS 3.1 base score of 7.7 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected Cisco Secure Firewall Adaptive Security Appliance (ASA) Software versions: 9.12.1; 9.12.1.2; 9.12.1.3, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.36% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Adaptive Security Appliance Software to 9.16.4.85 or 9.18.4.66 or 9.20.4 or 9.22.2.4, whichever matches your release line, or a later version.
- Update Secure Firewall Threat Defense to 7.0.9 or 7.2.11 or 7.4.3 or 7.6.4, whichever matches your release line, or a later version.
- Read the advisory on sec.cloudapps.cisco.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.12.1; 9.12.1.2; 9.12.1.3; 9.12.2; 9.12.2.4; 9.12.2.5; 9.12.2.9; 9.12.3; and 32 more ranges | Not stated |
| Cisco | Cisco Secure Firewall Threat Defense (FTD) Software | 6.4.0; 6.4.0.1; 6.4.0.3; 6.4.0.2; 6.4.0.4; 6.4.0.5; 6.4.0.6; 6.4.0.7; and 32 more ranges | Not stated |
| Cisco | Adaptive Security Appliance Software | 9.12.1 up to, but not including, 9.16.4.85; 9.17.1 up to, but not including, 9.18.4.66; 9.19.1 up to, but not including, 9.20.4; 9.22.1.1 up to, but not including, 9.22.2.4; 9.23.1 up to, but not including, 9.23.1.7 | 9.16.4.85, 9.18.4.66, 9.20.4, 9.22.2.4, 9.23.1.7 |
| Cisco | Secure Firewall Threat Defense | 6.4.0 up to, but not including, 7.0.9; 7.1.0 up to, but not including, 7.2.11; 7.3.0 up to, but not including, 7.4.3; 7.6.0 up to, but not including, 7.6.4; 7.7.0 up to, but not including, 7.7.11 | 7.0.9, 7.2.11, 7.4.3, 7.6.4, 7.7.11 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H. Scored by CNA (cisco.com).
Official description
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 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Missing Release of Memory after Effective Lifetime
The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.
How developers prevent this class of flaw
- Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone. For example, glibc in Linux provides protection against free of invalid pointers. When using Xcode to target OS X or iOS, enable automatic reference counting (ARC). To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Consider using the Boehm-Demers-Weiser garbage collector (bdwgc), which can help avoid leaks.
More Missing Release of Memory after Effective Lifetime vulnerabilities (CWE-401)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
- 8.6 High severity
- 8.8 High severity
- 8.1 High severity
- 8.4 High severity
- 8.8 High severity
- 9.9 Critical severity
Recent Missing Release of Memory after Effective Lifetime vulnerabilities
- 7.7 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 8.7 High severity
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