CyberSecBulletin
CVE-2025-20243NVD status: Deferred

Cisco Adaptive Security Appliance (ASA) Software: Loop with Unreachable Exit Condition

Published Updated By the CyberSecBulletin desk

CVE-2025-20243 is a high-severity loop with unreachable exit condition vulnerability in Cisco 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 Adaptive Security Appliance (ASA) Software versions: 9.12.3; 9.8.3; 9.12.1, 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 0.63% chance of exploitation within 30 days, higher than 51% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of Cisco Adaptive Security Appliance (ASA) Software you run against the affected versions below, and install the vendor's latest release.
  2. 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 Adaptive Security Appliance (ASA) Software9.12.3; 9.8.3; 9.12.1; 9.8.1; 9.12.2; 9.8.2.45; 9.8.2; 9.8.4; and 32 more rangesNot stated
CiscoCisco Firepower Threat Defense Software6.2.3.14; 6.4.0.1; 6.2.3.7; 6.2.3; 6.4.0.2; 6.2.3.9; 6.2.3.1; 6.2.3.2; and 32 more rangesNot stated

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 management and VPN web servers of Cisco Secure Firewall ASA Software and Secure FTD Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a DoS condition. This vulnerability is due to improper validation of user-supplied input on an interface with VPN web services. An attacker could exploit this vulnerability by sending crafted HTTP requests to a targeted web server on an affected device. A successful exploit could allow the attacker to cause a DoS condition when the device reloads.

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

The underlying weakness: Loop with Unreachable Exit Condition

The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

More Loop with Unreachable Exit Condition vulnerabilities (CWE-835)

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 Adaptive Security Appliance (ASA) Software

All Cisco Adaptive Security Appliance (ASA) Software vulnerabilities

Recent Loop with Unreachable Exit Condition vulnerabilities

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