Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-1023 Class Incomplete
Incomplete Comparison with Missing Factors
This weakness occurs when a program compares two items but fails to check all the necessary attributes that define their true relationship. The incomplete check can cause the software to treat…
Definition
What is CWE-1023?
This weakness occurs when a program compares two items but fails to check all the necessary attributes that define their true relationship. The incomplete check can cause the software to treat different items as identical or make incorrect security decisions.
Incomplete comparisons happen when a developer writes a check that only validates a subset of an object's or user's identity. For example, a system might authenticate a user by checking only a username without verifying the associated password or session token, or it might compare data objects using only an ID field while ignoring a critical 'type' or 'state' field. This creates a logical gap where two distinct entities can be incorrectly evaluated as equivalent.
This flaw directly undermines security and logic by allowing unauthorized access, privilege escalation, or data corruption. Attackers can exploit it by providing an entity that matches on the checked factors but differs maliciously on the unchecked ones. To prevent this, always ensure comparison functions validate every unique and security-relevant property that defines an entity's complete identity within that specific context.
Real-world impact
Real-world CVEs caused by CWE-1023
-
PHP remote file inclusion in web application that filters "http" and "https" URLs, but not "ftp".
-
Product does not prevent access to restricted directories due to partial string comparison with a public directory
How attackers exploit it
Step-by-step attacker path
- 1
Consider an application in which Truck objects are defined to be the same if they have the same make, the same model, and were manufactured in the same year.
- 2
Here, the equals() method only checks the make and model of the Truck objects, but the year of manufacture is not included.
- 3
This example defines a fixed username and password. The AuthenticateUser() function is intended to accept a username and a password from an untrusted user, and check to ensure that it matches the username and password. If the username and password match, AuthenticateUser() is intended to indicate that authentication succeeded.
- 4
In AuthenticateUser(), the strncmp() call uses the string length of an attacker-provided inPass parameter in order to determine how many characters to check in the password. So, if the attacker only provides a password of length 1, the check will only examine the first byte of the application's password before determining success.
- 5
As a result, this partial comparison leads to improper authentication (CWE-287).
Vulnerable code example
Vulnerable Java
Consider an application in which Truck objects are defined to be the same if they have the same make, the same model, and were manufactured in the same year.
public class Truck {
private String make;
private String model;
private int year;
public boolean equals(Object o) {
if (o == null) return false;
if (o == this) return true;
if (!(o instanceof Truck)) return false;
Truck t = (Truck) o;
return (this.make.equals(t.getMake()) && this.model.equals(t.getModel()));
}
} Attacker payload
Any of these passwords would still cause authentication to succeed for the "admin" user:
p
pa
pas
pass Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-1023
- Testing Thoroughly test the comparison scheme before deploying code into production. Perform positive testing as well as negative testing.
Detection signals
How to detect CWE-1023
Run dynamic application security testing against the live endpoint.
Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.
Code review: flag any new code that handles input from this surface without using the validated framework helpers.
Plexicus auto-detects CWE-1023 and opens a fix PR in under 60 seconds.
Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.
Frequently asked questions What is CWE-1023?
How serious is CWE-1023?
What languages or platforms are affected by CWE-1023?
How can I prevent CWE-1023?
How does Plexicus detect and fix CWE-1023?
Where can I learn more about CWE-1023?
Frequently asked questions
What is CWE-1023?
This weakness occurs when a program compares two items but fails to check all the necessary attributes that define their true relationship. The incomplete check can cause the software to treat different items as identical or make incorrect security decisions.
How serious is CWE-1023?
MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.
What languages or platforms are affected by CWE-1023?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-1023?
Thoroughly test the comparison scheme before deploying code into production. Perform positive testing as well as negative testing.
How does Plexicus detect and fix CWE-1023?
Plexicus's SAST engine matches the data-flow signature for CWE-1023 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-1023?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/1023.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-1023
CWE-697 Parent
Incorrect Comparison
This weakness occurs when a security-critical decision relies on a flawed comparison between two pieces of data. The incorrect logic can…
CWE-1024 Sibling
Comparison of Incompatible Types
This vulnerability occurs when code directly compares two values of fundamentally different data types, which can lead to unreliable or…
CWE-1025 Sibling
Comparison Using Wrong Factors
This weakness occurs when a program compares two items but checks the wrong properties or attributes. This flawed comparison leads to…
CWE-1039 Sibling
Inadequate Detection or Handling of Adversarial Input Perturbations in Automated Recognition Mechanism
This vulnerability occurs when a system uses automated AI or machine learning to classify complex inputs like images, audio, or text, but…
CWE-1077 Sibling
Floating Point Comparison with Incorrect Operator
This vulnerability occurs when code compares two floating-point numbers using direct equality operators (like == or !=) without accounting…
CWE-1254 Sibling
Incorrect Comparison Logic Granularity
This vulnerability occurs when a system compares sensitive data, like passwords or authentication tokens, piece-by-piece instead of as a…
CWE-183 Sibling
Permissive List of Allowed Inputs
This vulnerability occurs when an application's security filter uses an allowlist that is too broad, mistakenly permitting dangerous…
CWE-185 Sibling
Incorrect Regular Expression
This vulnerability occurs when a regular expression is written incorrectly, causing it to match or validate data in unintended and…
CWE-581 Sibling
Object Model Violation: Just One of Equals and Hashcode Defined
This vulnerability occurs when a Java class defines either the equals() method or the hashCode() method, but not both, breaking a…
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