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CWE-602 Class Draft
Client-Side Enforcement of Server-Side Security
This vulnerability occurs when a server incorrectly trusts the client to enforce critical security rules, such as input validation or access controls, instead of performing these checks itself.
Definition
What is CWE-602?
This vulnerability occurs when a server incorrectly trusts the client to enforce critical security rules, such as input validation or access controls, instead of performing these checks itself.
This flaw creates a fundamental trust issue. Since an attacker has full control over their own client—whether it's a browser, mobile app, or API client—they can easily bypass, remove, or manipulate any client-side security checks. The server, operating under the false assumption that these checks are reliable, then processes malicious or unauthorized requests.
The impact depends entirely on what the client was supposed to protect. Common consequences include unauthorized data access, privilege escalation, data corruption, or complete system compromise. The root cause is a design error: security must always be enforced at the point where trust is established and data is ultimately processed—the server.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-602
-
SCADA system only uses client-side authentication, allowing adversaries to impersonate other users.
-
ASP program allows upload of .asp files by bypassing client-side checks.
-
steganography products embed password information in the carrier file, which can be extracted from a modified client.
-
steganography products embed password information in the carrier file, which can be extracted from a modified client.
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client allows server to modify client's configuration and overwrite arbitrary files.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
This example contains client-side code that checks if the user authenticated successfully before sending a command. The server-side code performs the authentication in one step, and executes the command in a separate step.
- 2
CLIENT-SIDE (client.pl)
- 3
SERVER-SIDE (server.pl):
- 4
The server accepts 2 commands, "AUTH" which authenticates the user, and "CHANGE-ADDRESS" which updates the address field for the username. The client performs the authentication and only sends a CHANGE-ADDRESS for that user if the authentication succeeds. Because the client has already performed the authentication, the server assumes that the username in the CHANGE-ADDRESS is the same as the authenticated user. An attacker could modify the client by removing the code that sends the "AUTH" command and simply executing the CHANGE-ADDRESS.
- 5
In 2022, the OT:ICEFALL study examined products by 10 different Operational Technology (OT) vendors. The researchers reported 56 vulnerabilities and said that the products were "insecure by design" [REF-1283]. If exploited, these vulnerabilities often allowed adversaries to change how the products operated, ranging from denial of service to changing the code that the products executed. Since these products were often used in industries such as power, electrical, water, and others, there could even be safety implications.
Verwundbares Codebeispiel
Vulnerable Perl
SERVER-SIDE (server.pl):
$sock = acceptSocket(1234);
($cmd, $args) = ParseClientRequest($sock);
if ($cmd eq "AUTH") {
($username, $pass) = split(/\s+/, $args, 2);
$result = AuthenticateUser($username, $pass);
writeSocket($sock, "$result\n");
```
# does not close the socket on failure; assumes the*
*# user will try again*
}
elsif ($cmd eq "CHANGE-ADDRESS") {
```
if (validateAddress($args)) {
$res = UpdateDatabaseRecord($username, "address", $args);
writeSocket($sock, "SUCCESS\n");
}
else {
writeSocket($sock, "FAILURE -- address is malformed\n");
}
} Sicheres Codebeispiel
Secure Perl
CLIENT-SIDE (client.pl)
$server = "server.example.com";
$username = AskForUserName();
$password = AskForPassword();
$address = AskForAddress();
$sock = OpenSocket($server, 1234);
writeSocket($sock, "AUTH $username $password\n");
$resp = readSocket($sock);
if ($resp eq "success") {
```
# username/pass is valid, go ahead and update the info!*
writeSocket($sock, "CHANGE-ADDRESS $username $address\n";}
else {
```
print "ERROR: Invalid Authentication!\n";
} 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-602
- Architecture and Design For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server. Even though client-side checks provide minimal benefits with respect to server-side security, they are still useful. First, they can support intrusion detection. If the server receives input that should have been rejected by the client, then it may be an indication of an attack. Second, client-side error-checking can provide helpful feedback to the user about the expectations for valid input. Third, there may be a reduction in server-side processing time for accidental input errors, although this is typically a small savings.
- Architecture and Design If some degree of trust is required between the two entities, then use integrity checking and strong authentication to ensure that the inputs are coming from a trusted source. Design the product so that this trust is managed in a centralized fashion, especially if there are complex or numerous communication channels, in order to reduce the risks that the implementer will mistakenly omit a check in a single code path.
- Testing Use dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
- Testing Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.
Erkennungssignale
How to detect CWE-602
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-602 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-602?
Wie gravierend ist CWE-602?
Welche Sprachen oder Plattformen sind von CWE-602 betroffen?
Wie kann ich CWE-602 verhindern?
Wie erkennt und behebt Plexicus CWE-602?
Wo erfahre ich mehr über CWE-602?
Frequently asked questions
Was ist CWE-602?
This vulnerability occurs when a server incorrectly trusts the client to enforce critical security rules, such as input validation or access controls, instead of performing these checks itself.
Wie gravierend ist CWE-602?
MITRE stuft die Exploit-Wahrscheinlichkeit als mittel ein — eine Ausnutzung ist realistisch, erfordert aber meist bestimmte Bedingungen.
Welche Sprachen oder Plattformen sind von CWE-602 betroffen?
MITRE lists the following affected platforms: ICS/OT, Mobile.
Wie kann ich CWE-602 verhindern?
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server. Even though client-side checks provide minimal benefits with respect to server-side security, they are still useful. First, they can support…
Wie erkennt und behebt Plexicus CWE-602?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-602 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-602?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/602.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-602
CWE-693 Parent
Protection Mechanism Failure
This weakness occurs when software either lacks a necessary security control, implements one that is too weak, or fails to activate an…
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-1248 Sibling
Semiconductor Defects in Hardware Logic with Security-Sensitive Implications
A security-critical hardware component contains physical flaws in its semiconductor material, which can cause it to malfunction and…
CWE-1253 Sibling
Incorrect Selection of Fuse Values
This vulnerability occurs when a hardware security fuse is incorrectly programmed to represent a 'secure' state as logic 0 (unblown). An…
CWE-1269 Sibling
Product Released in Non-Release Configuration
This vulnerability occurs when a product ships to customers while still configured with its pre-production or manufacturing settings,…
CWE-1278 Sibling
Missing Protection Against Hardware Reverse Engineering Using Integrated Circuit (IC) Imaging Techniques
This vulnerability occurs when hardware lacks safeguards against physical inspection, allowing attackers to extract sensitive data by…
CWE-1291 Sibling
Public Key Re-Use for Signing both Debug and Production Code
This vulnerability occurs when the same cryptographic key is used to sign both development/debug software builds and final production…
CWE-1318 Sibling
Missing Support for Security Features in On-chip Fabrics or Buses
This vulnerability occurs when the communication channels (fabrics or buses) within a chip lack built-in or enabled security features,…
CWE-1319 Sibling
Improper Protection against Electromagnetic Fault Injection (EM-FI)
This vulnerability occurs when a hardware device lacks sufficient shielding against electromagnetic interference, allowing attackers to…
Ressourcen
Further reading
- MITRE — offizielle CWE-602 https://cwe.mitre.org/data/definitions/602.html
- Writing Secure Code https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223
- OT:ICEFALL: The legacy of "insecure by design" and its implications for certifications and risk management https://www.forescout.com/resources/ot-icefall-report/
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