Overview
The cybersecurity community has recently identified a critical vulnerability, CVE-2025-20263, that affects Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software. This vulnerability has the potential to compromise the stability and security of systems running these applications, making it a significant threat to organizations that rely on Cisco’s secure firewall services. Its severity is underscored by its high CVSS score and the potential for system compromise or data leakage.
Vulnerability Summary
CVE ID: CVE-2025-20263
Severity: Critical (8.6 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: A successful exploit could cause a buffer overflow condition that leads to a system reload, resulting in a denial of service (DoS) condition. This could potentially lead to system compromise or data leakage.
Affected Products
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Product | Affected Versions
Cisco Secure Firewall ASA Software | All current versions until patched
Cisco Secure Firewall FTD Software | All current versions until patched
How the Exploit Works
The vulnerability is due to insufficient boundary checks for specific data provided to the web services interface of an affected system. An attacker could exploit this vulnerability by sending a maliciously crafted HTTP request to the affected system. The improper boundary checks facilitate a buffer overflow condition, causing the system to reload and leading to a DoS condition.
Conceptual Example Code
Below is a conceptual example of how an attacker might exploit this vulnerability using a malicious HTTP request:
POST /asa_endpoint HTTP/1.1
Host: target.example.com
Content-Type: application/xml
{ "payload": "<!-[malicious XML data exceeding buffer capacity]->" }In this example, the attacker sends a POST request with a payload containing XML data that exceeds the buffer capacity of the system’s web services interface. This triggers a buffer overflow condition, which in turn causes the system to reload and results in a denial of service.
Mitigation Guidance
Users are advised to apply vendor patches as soon as they become available to remediate this vulnerability. In the absence of a patch, users can utilize Web Application Firewall (WAF) or Intrusion Detection Systems (IDS) as temporary mitigation measures. These tools can help to monitor network traffic for malicious activity and prevent any potential exploitation of this vulnerability.