Description
The product receives an input value that is used as a resource identifier or other type of reference, but it does not validate or incorrectly validates that the input is equivalent to a potentially-unsafe value.
Attackers can sometimes bypass input validation schemes by finding inputs that appear to be safe, but will be dangerous when processed at a lower layer or by a downstream component. For example, a simple XSS protection mechanism might try to validate that an input has no "<script>" tags using case-sensitive matching, but since HTML is case-insensitive when processed by web browsers, an attacker could inject "<ScrIpT>" and trigger XSS.
Potential Impact
Other
Varies by Context
Mitigations & Prevention
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across relat
Real-World CVE Examples
| CVE ID | Description |
|---|---|
| CVE-2021-39155 | Chain: A microservice integration and management platform compares the hostname in the HTTP Host header in a case-sensitive way (CWE-178, CWE-1289), allowing bypass of the authorization policy (CWE-86 |
| CVE-2020-11053 | Chain: Go-based Oauth2 reverse proxy can send the authenticated user to another site at the end of the authentication flow. A redirect URL with HTML-encoded whitespace characters can bypass the valida |
| CVE-2005-0269 | File extension check in forum software only verifies extensions that contain all lowercase letters, which allows remote attackers to upload arbitrary files via file extensions that include uppercase l |
| CVE-2001-1238 | Task Manager does not allow local users to end processes with uppercase letters named (1) winlogon.exe, (2) csrss.exe, (3) smss.exe and (4) services.exe via the Process tab which could allow local use |
| CVE-2004-2214 | HTTP server allows bypass of access restrictions using URIs with mixed case. |
Related Weaknesses
Frequently Asked Questions
What is CWE-1289?
CWE-1289 (Improper Validation of Unsafe Equivalence in Input) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. The product receives an input value that is used as a resource identifier or other type of reference, but it does not validate or incorrectly validates that the input is equivalent to a potentially-un...
How can CWE-1289 be exploited?
Attackers can exploit CWE-1289 (Improper Validation of Unsafe Equivalence in Input) to varies by context. This weakness is typically introduced during the Implementation phase of software development.
How do I prevent CWE-1289?
Key mitigations include: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not stric
What is the severity of CWE-1289?
CWE-1289 is classified as a Base-level weakness (Medium abstraction). It has been observed in 5 real-world CVEs.