A vulnerability in the implementation of the direct authentication feature in Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause an affected device to unexpectedly reload, resulting in a denial of service (DoS) condition. The vulnerability is due to incomplete input validation of the HTTP header. An attacker could exploit this vulnerability by sending a crafted HTTP request to the local IP address of an affected device. A successful exploit could allow the attacker to cause the affected device to reload. This vulnerability affects Cisco Adaptive Security Appliance (ASA) Software that is running on the following Cisco products: ASA 5500 Series Adaptive Security Appliances, ASA 5500-X Series Next-Generation Firewalls, ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers, ASA 1000V Cloud Firewall, Adaptive Security Virtual Appliance (ASAv), Firepower 4110 Security Appliance, Firepower 9300 ASA Security Module, ISA 3000 Industrial Security Appliance. Cisco Bug IDs: CSCvd59063.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Adaptive_security_appliance_software | Cisco | 9.4(3) (including) | 9.4(3) (including) |
| Adaptive_security_appliance_software | Cisco | 9.7(1) (including) | 9.7(1) (including) |
| Adaptive_security_appliance_software | Cisco | 9.8(0.56) (including) | 9.8(0.56) (including) |
Input validation is a frequently-used technique for checking potentially dangerous inputs in order to ensure that the inputs are safe for processing within the code, or when communicating with other components. When software does not validate input properly, an attacker is able to craft the input in a form that is not expected by the rest of the application. This will lead to parts of the system receiving unintended input, which may result in altered control flow, arbitrary control of a resource, or arbitrary code execution. Input validation is not the only technique for processing input, however. Other techniques attempt to transform potentially-dangerous input into something safe, such as filtering (CWE-790) - which attempts to remove dangerous inputs - or encoding/escaping (CWE-116), which attempts to ensure that the input is not misinterpreted when it is included in output to another component. Other techniques exist as well (see CWE-138 for more examples.) Input validation can be applied to:
Data can be simple or structured. Structured data can be composed of many nested layers, composed of combinations of metadata and raw data, with other simple or structured data. Many properties of raw data or metadata may need to be validated upon entry into the code, such as:
Implied or derived properties of data must often be calculated or inferred by the code itself. Errors in deriving properties may be considered a contributing factor to improper input validation.
Note that “input validation” has very different meanings to different people, or within different classification schemes. Caution must be used when referencing this CWE entry or mapping to it. For example, some weaknesses might involve inadvertently giving control to an attacker over an input when they should not be able to provide an input at all, but sometimes this is referred to as input validation. Finally, it is important to emphasize that the distinctions between input validation and output escaping are often blurred, and developers must be careful to understand the difference, including how input validation is not always sufficient to prevent vulnerabilities, especially when less stringent data types must be supported, such as free-form text. Consider a SQL injection scenario in which a person’s last name is inserted into a query. The name “O’Reilly” would likely pass the validation step since it is a common last name in the English language. However, this valid name cannot be directly inserted into the database because it contains the “’” apostrophe character, which would need to be escaped or otherwise transformed. In this case, removing the apostrophe might reduce the risk of SQL injection, but it would produce incorrect behavior because the wrong name would be recorded.