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CWE-697 Pillar Incomplete
Incorrect Comparison
This weakness occurs when a security-critical decision relies on a flawed comparison between two pieces of data. The incorrect logic can create a gap that attackers exploit to bypass checks or…
Definition
What is CWE-697?
This weakness occurs when a security-critical decision relies on a flawed comparison between two pieces of data. The incorrect logic can create a gap that attackers exploit to bypass checks or trigger unintended behavior.
Incorrect comparisons often happen because the check is too simplistic for the security context. For example, a developer might validate only one attribute when multiple factors should be considered, compare the wrong values entirely, or implement the comparison logic incorrectly (like using the wrong operator). This creates a mismatch between the intended security rule and what the code actually enforces.
From a developer's perspective, this flaw is a logic bug in a security gate. It's not about missing a check, but about writing a check that doesn't work as intended. To prevent it, carefully review any comparison used for authentication, authorization, input validation, or state change decisions. Ensure it evaluates all necessary conditions with precise logic and test it with both valid and malicious edge cases.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-697
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Chain: Python-based HTTP Proxy server uses the wrong boolean operators (CWE-480) causing an incorrect comparison (CWE-697) that identifies an authN failure if all three conditions are met instead of only one, allowing bypass of the proxy authentication (CWE-1390)
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Chain: Proxy uses a substring search instead of parsing the Transfer-Encoding header (CWE-697), allowing request splitting (CWE-113) and cache poisoning
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Proxy performs incorrect comparison of request headers, leading to infoleak
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 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).
Verwundbares Codebeispiel
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()));
}
} Angreifer-Payload
Any of these passwords would still cause authentication to succeed for the "admin" user:
p
pa
pas
pass Sicheres Codebeispiel
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.
Präventions-Checkliste
How to prevent CWE-697
- Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
- Implementation Validate input at trust boundaries; use allowlists, not denylists.
- Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
- Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
- Operation Monitor logs for the runtime signals listed in the next section.
Erkennungssignale
How to detect CWE-697
Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.
Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.
Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.
Plexicus erkennt CWE-697 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.
Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.
Häufig gestellte Fragen Was ist CWE-697?
Wie gravierend ist CWE-697?
Welche Sprachen oder Plattformen sind von CWE-697 betroffen?
Wie kann ich CWE-697 verhindern?
Wie erkennt und behebt Plexicus CWE-697?
Wo erfahre ich mehr über CWE-697?
Frequently asked questions
Was ist CWE-697?
This weakness occurs when a security-critical decision relies on a flawed comparison between two pieces of data. The incorrect logic can create a gap that attackers exploit to bypass checks or trigger unintended behavior.
Wie gravierend ist CWE-697?
MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.
Welche Sprachen oder Plattformen sind von CWE-697 betroffen?
MITRE lists the following affected platforms: Not Technology-Specific.
Wie kann ich CWE-697 verhindern?
Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.
Wie erkennt und behebt Plexicus CWE-697?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-697 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.
Wo erfahre ich mehr über CWE-697?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/697.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-697
CWE-1023 Child
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…
CWE-1024 Child
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 Child
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 Child
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 Child
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 Child
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 Child
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 Child
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 Child
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…
Ressourcen
Further reading
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