CWE-99 Class Draft High likelihood

Improper Control of Resource Identifiers ('Resource Injection')

This vulnerability occurs when an application accepts user input as a resource identifier (like a file path or port number) without proper validation, allowing an attacker to access or manipulate…

Definition

What is CWE-99?

This vulnerability occurs when an application accepts user input as a resource identifier (like a file path or port number) without proper validation, allowing an attacker to access or manipulate resources outside the intended scope.
A resource injection flaw arises when two conditions are met. First, an attacker can control the identifier used to access a system resource, such as part of a filename, a database key, a network port, or a configuration setting. Second, by controlling this identifier, the attacker gains unauthorized capabilities—like reading sensitive files, overwriting protected data, redirecting network traffic, or altering application behavior—that would normally be restricted. In practice, this happens because the application treats unvalidated user input as a direct reference to a resource. For example, an attacker might supply a path like '../../etc/passwd' to traverse directories, or specify a remote server address to exfiltrate data. The core failure is a lack of input validation and authorization checks before the resource is accessed, effectively letting users dictate which system resources the application uses.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-99

  • CVE-2013-4787

    chain: mobile OS verifies cryptographic signature of file in an archive, but then installs a different file with the same name that is also listed in the archive.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    The following Java code uses input from an HTTP request to create a file name. The programmer has not considered the possibility that an attacker could provide a file name such as "../../tomcat/conf/server.xml", which causes the application to delete one of its own configuration files.

  2. 2

    The following code uses input from the command line to determine which file to open and echo back to the user. If the program runs with privileges and malicious users can create soft links to the file, they can use the program to read the first part of any file on the system.

  3. 3

    The kind of resource the data affects indicates the kind of content that may be dangerous. For example, data containing special characters like period, slash, and backslash, are risky when used in methods that interact with the file system. (Resource injection, when it is related to file system resources, sometimes goes by the name "path manipulation.") Similarly, data that contains URLs and URIs is risky for functions that create remote connections.

Verwundbares Codebeispiel

Vulnerable Java

The following Java code uses input from an HTTP request to create a file name. The programmer has not considered the possibility that an attacker could provide a file name such as "../../tomcat/conf/server.xml", which causes the application to delete one of its own configuration files.

Verwundbar Java 
String rName = request.getParameter("reportName");
  File rFile = new File("/usr/local/apfr/reports/" + rName);
  ...
  rFile.delete();
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-99

  • Implementation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, it can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Erkennungssignale

How to detect CWE-99

Automated Static Analysis High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Plexicus Auto-Fix

Plexicus erkennt CWE-99 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-99?

This vulnerability occurs when an application accepts user input as a resource identifier (like a file path or port number) without proper validation, allowing an attacker to access or manipulate resources outside the intended scope.

Wie gravierend ist CWE-99?

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-99 betroffen?

MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.

Wie kann ich CWE-99 verhindern?

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and…

Wie erkennt und behebt Plexicus CWE-99?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-99 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-99?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/99.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-99

CWE-74 Parent

Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

This vulnerability occurs when an application uses untrusted external input to build a command, query, or data structure for another…

CWE-1236 Sibling

Improper Neutralization of Formula Elements in a CSV File

This vulnerability occurs when an application writes user-supplied data into a CSV file without properly sanitizing special characters.…

CWE-75 Sibling

Failure to Sanitize Special Elements into a Different Plane (Special Element Injection)

This vulnerability occurs when an application fails to properly filter or encode user-supplied data containing special characters or…

CWE-77 Sibling

Improper Neutralization of Special Elements used in a Command ('Command Injection')

This vulnerability occurs when an application builds a system command using untrusted user input without properly sanitizing it. An…

CWE-78 Sibling

Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

OS Command Injection occurs when an application builds a system command using untrusted, external input without properly sanitizing it.…

CWE-79 Sibling

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

This vulnerability occurs when a web application fails to properly sanitize or encode user-supplied input before displaying it on a…

CWE-88 Sibling

Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

This vulnerability occurs when an application builds a command string for execution by another component, but fails to properly separate…

CWE-89 Sibling

Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')

SQL Injection occurs when an application builds a database query using untrusted user input without properly sanitizing it. This allows an…

CWE-91 Sibling

XML Injection (aka Blind XPath Injection)

XML Injection occurs when an application fails to properly validate or escape user-controlled input before including it in XML documents…

Ressourcen

Further reading

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