CWE-784 Variant Draft High likelihood

Reliance on Cookies without Validation and Integrity Checking in a Security Decision

This vulnerability occurs when an application makes security decisions—like granting access or verifying identity—based solely on cookie data without first confirming the cookie's authenticity or…

Definition

What is CWE-784?

Attackers can easily manipulate cookie values directly in the browser or by crafting custom client-side requests. Since the application trusts this data without validation, attackers can forge cookies to impersonate other users, bypass login screens, or escalate their privileges by inserting expected values. To prevent this, developers must never treat cookies as a trusted security mechanism on their own. Always validate and verify cookie integrity on the server using techniques like cryptographic signing, comparing against server-side sessions, or using secure, tamper-proof tokens instead of plain data.

Auswirkungen in der Praxis

Real-world CVEs caused by CWE-784

CVE-2009-1549

Attacker can bypass authentication by setting a cookie to a specific value.
CVE-2009-1619

Attacker can bypass authentication and gain admin privileges by setting an "admin" cookie to 1.
CVE-2009-0864

Content management system allows admin privileges by setting a "login" cookie to "OK."
CVE-2008-5784

e-dating application allows admin privileges by setting the admin cookie to 1.
CVE-2008-6291

Web-based email list manager allows attackers to gain admin privileges by setting a login cookie to "admin."

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

1
The following code excerpt reads a value from a browser cookie to determine the role of the user.
2
The following code could be for a medical records application. It performs authentication by checking if a cookie has been set.
3
The programmer expects that the AuthenticateUser() check will always be applied, and the "authenticated" cookie will only be set when authentication succeeds. The programmer even diligently specifies a 2-hour expiration for the cookie.
4
However, the attacker can set the "authenticated" cookie to a non-zero value such as 1. As a result, the $auth variable is 1, and the AuthenticateUser() check is not even performed. The attacker has bypassed the authentication.
5
In the following example, an authentication flag is read from a browser cookie, thus allowing for external control of user state data.

Verwundbares Codebeispiel

Vulnerable Java

The following code excerpt reads a value from a browser cookie to determine the role of the user.

Verwundbar Java

Cookie[] cookies = request.getCookies();
  for (int i =0; i< cookies.length; i++) {
  	Cookie c = cookies[i];
  	if (c.getName().equals("role")) {
  		userRole = c.getValue();
  	}
  }

Sicheres Codebeispiel

Secure pseudo

Sicher 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-784

Architecture and Design Avoid using cookie data for a security-related decision.
Implementation Perform thorough input validation (i.e.: server side validation) on the cookie data if you're going to use it for a security related decision.
Architecture and Design Add integrity checks to detect tampering.
Architecture and Design Protect critical cookies from replay attacks, since cross-site scripting or other attacks may allow attackers to steal a strongly-encrypted cookie that also passes integrity checks. This mitigation applies to cookies that should only be valid during a single transaction or session. By enforcing timeouts, you may limit the scope of an attack. As part of your integrity check, use an unpredictable, server-side value that is not exposed to the client.

Erkennungssignale

How to detect CWE-784

SAST High

Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.

DAST Moderate

Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.

Runtime Moderate

Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.

Code review Moderate

Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.

Plexicus Auto-Fix

Plexicus erkennt CWE-784 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.

Demo anfordern Plexicus kostenlos testen

Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-784?

Wie gravierend ist CWE-784?

MITRE stuft die Exploit-Wahrscheinlichkeit als hoch ein — diese Schwachstelle wird aktiv in freier Wildbahn ausgenutzt und sollte priorisiert behoben werden.

Welche Sprachen oder Plattformen sind von CWE-784 betroffen?

MITRE lists the following affected platforms: Web Based.

Wie kann ich CWE-784 verhindern?

Avoid using cookie data for a security-related decision. Perform thorough input validation (i.e.: server side validation) on the cookie data if you're going to use it for a security related decision.

Wie erkennt und behebt Plexicus CWE-784?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-784 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-784?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/784.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-784

CWE-565 Parent