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CWE-6 Variant Incomplete
J2EE Misconfiguration: Insufficient Session-ID Length
This vulnerability occurs when a J2EE application uses session identifiers that are too short, making them easier for attackers to predict or capture.
Definition
What is CWE-6?
This vulnerability occurs when a J2EE application uses session identifiers that are too short, making them easier for attackers to predict or capture.
Session IDs that are too short drastically reduce the number of possible combinations, making them vulnerable to brute-force guessing or enumeration attacks. When an attacker successfully guesses or steals a valid session ID, they can impersonate the legitimate user and hijack their active session, potentially gaining unauthorized access to sensitive data or privileged functions.
To prevent this, developers must ensure session IDs are generated with sufficient length and entropy, typically using a secure random number generator. Longer session IDs exponentially increase the possible values, making them computationally infeasible to guess and significantly raising the security barrier against session hijacking attempts.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-6
Bisher sind in MITREs Katalog keine öffentlichen CVE-Referenzen mit dieser CWE verknüpft.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
The following XML example code is a deployment descriptor for a Java web application deployed on a Sun Java Application Server. This deployment descriptor includes a session configuration property for configuring the session ID length.
- 2
This deployment descriptor has set the session ID length for this Java web application to 8 bytes (or 64 bits). The session ID length for Java web applications should be set to 16 bytes (128 bits) to prevent attackers from guessing and/or stealing a session ID and taking over a user's session.
- 3
Note for most application servers including the Sun Java Application Server the session ID length is by default set to 128 bits and should not be changed. And for many application servers the session ID length cannot be changed from this default setting. Check your application server documentation for the session ID length default setting and configuration options to ensure that the session ID length is set to 128 bits.
Verwundbares Codebeispiel
Vulnerable XML
The following XML example code is a deployment descriptor for a Java web application deployed on a Sun Java Application Server. This deployment descriptor includes a session configuration property for configuring the session ID length.
<sun-web-app>
...
<session-config>
<session-properties>
<property name="idLengthBytes" value="8">
<description>The number of bytes in this web module's session ID.</description>
</property>
</session-properties>
</session-config>
...
</sun-web-app> 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-6
- Implementation Session identifiers should be at least 128 bits long to prevent brute-force session guessing. A shorter session identifier leaves the application open to brute-force session guessing attacks.
- Implementation A lower bound on the number of valid session identifiers that are available to be guessed is the number of users that are active on a site at any given moment. However, any users that abandon their sessions without logging out will increase this number. (This is one of many good reasons to have a short inactive session timeout.) With a 64 bit session identifier, assume 32 bits of entropy. For a large web site, assume that the attacker can try 1,000 guesses per second and that there are 10,000 valid session identifiers at any given moment. Given these assumptions, the expected time for an attacker to successfully guess a valid session identifier is less than 4 minutes. Now assume a 128 bit session identifier that provides 64 bits of entropy. With a very large web site, an attacker might try 10,000 guesses per second with 100,000 valid session identifiers available to be guessed. Given these assumptions, the expected time for an attacker to successfully guess a valid session identifier is greater than 292 years.
Erkennungssignale
How to detect CWE-6
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.
CWE-6
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Häufig gestellte Fragen Was ist CWE-6?
Wie gravierend ist CWE-6?
Welche Sprachen oder Plattformen sind von CWE-6 betroffen?
Wie kann ich CWE-6 verhindern?
Wie erkennt und behebt Plexicus CWE-6?
Wo erfahre ich mehr über CWE-6?
Frequently asked questions
Was ist CWE-6?
This vulnerability occurs when a J2EE application uses session identifiers that are too short, making them easier for attackers to predict or capture.
Wie gravierend ist CWE-6?
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-6 betroffen?
MITRE lists the following affected platforms: Java.
Wie kann ich CWE-6 verhindern?
Session identifiers should be at least 128 bits long to prevent brute-force session guessing. A shorter session identifier leaves the application open to brute-force session guessing attacks. A lower bound on the number of valid session identifiers that are available to be guessed is the number of users that are active on a site at any given moment. However, any users that abandon their sessions without logging out will increase this number. (This is one of many good reasons to have a short…
Wie erkennt und behebt Plexicus CWE-6?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-6 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-6?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/6.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-6
Ressourcen
Further reading
- MITRE — offizielle CWE-6 https://cwe.mitre.org/data/definitions/6.html
- Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
- Hold Your Sessions: An Attack on Java Session-id Generation https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/gm05.pdf
Bereit, das Wesentliche zu validieren?
Bereit zu validieren, was zählt.
Plexicus ist Proof-Driven AppSec: validierte Funde, kontextuelles Verständnis und geprüfte Remediation — in Evidenz verankert, mit Ihnen gescoped.