CyberSecBulletin
CVE-2026-20103NVD status: Analyzed

Cisco Secure Firewall Adaptive Security…: Allocation of Resources Without Limits or Throttling

Published Updated By the CyberSecBulletin desk

CVE-2026-20103 is a high-severity allocation of resources without limits or throttling vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software from Cisco, with a CVSS 3.1 base score of 8.6 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Cisco Secure Firewall Adaptive Security Appliance (ASA) Software versions: 9.12.4.48; 9.12.4.50; 9.12.4.52, 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 0.4% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. 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.
  2. 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.
  3. Read the advisory on sec.cloudapps.cisco.com for workarounds and exact fixed builds.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
CiscoCisco Secure Firewall Adaptive Security Appliance (ASA) Software9.12.4.48; 9.12.4.50; 9.12.4.52; 9.12.4.54; 9.12.4.55; 9.12.4.56; 9.12.4.58; 9.12.4.62; and 32 more rangesNot stated
CiscoCisco Secure Firewall Threat Defense (FTD) Software6.4.0.16; 6.4.0.17; 6.4.0.18; 7.0.4; 7.0.5; 7.0.6; 7.0.6.1; 7.0.6.2; and 32 more rangesNot stated
CiscoAdaptive Security Appliance Software9.12.1 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, 9.23.1.79.16.4.85, 9.18.4.66, 9.20.4, 9.22.2.4, 9.23.1.7
CiscoSecure Firewall Threat Defense6.4.0 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, 7.7.117.0.9, 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
NoneNo account or login is needed.
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:N/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 unauthenticated, remote attacker to exhaust device memory resulting in a denial of service (DoS) condition to new Remote Access SSL VPN connections. This does not affect the management interface, though it may become temporarily unresponsive. 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 web interface to stop responding, resulting in a DoS condition.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Allocation of Resources Without Limits or Throttling

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

How developers prevent this class of flaw

  • Clearly specify the minimum and maximum expectations for capabilities, and dictate which behaviors are acceptable when resource allocation reaches limits.
  • Limit the amount of resources that are accessible to unprivileged users. Set per-user limits for resources. Allow the system administrator to define these limits. Be careful to avoid CWE-410.
  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

More Allocation of Resources Without Limits or Throttling vulnerabilities (CWE-770)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software

All Cisco Secure Firewall Adaptive Security Appliance (ASA) Software vulnerabilities

Recent Allocation of Resources Without Limits or Throttling vulnerabilities

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