CWE-250 Base Rascunho Medium likelihood

Execution with Unnecessary Privileges

This vulnerability occurs when software runs with higher permissions than it actually needs to perform its tasks. This excessive privilege creates security risks by opening doors to new attacks or…

Definição

What is CWE-250?

This vulnerability occurs when software runs with higher permissions than it actually needs to perform its tasks. This excessive privilege creates security risks by opening doors to new attacks or making existing weaknesses more dangerous.

Think of it like giving a hotel guest a master key to the entire building when they only need access to their room. When applications or services run with elevated privileges (like root or SYSTEM), a simple bug or compromise can have catastrophic consequences. An attacker who exploits a flaw in this over-privileged component gains those same high-level permissions, allowing them to install malware, steal sensitive data, or disable security controls across the entire system. To prevent this, developers should follow the principle of least privilege (PoLP). This means explicitly configuring each component to run with the minimum permissions required for its specific function. In practice, this involves using service accounts with restricted rights, dropping privileges after initialization, and separating high-privilege tasks into isolated, minimal processes. Regular privilege audits are essential to ensure configurations don't drift over time toward excessive access.

Vulnerability Diagram CWE-250

Impacto no mundo real

Real-world CVEs caused by CWE-250

CVE-2007-4217

FTP client program on a certain OS runs with setuid privileges and has a buffer overflow. Most clients do not need extra privileges, so an overflow is not a vulnerability for those clients.
CVE-2008-1877

Program runs with privileges and calls another program with the same privileges, which allows read of arbitrary files.
CVE-2007-5159

OS incorrectly installs a program with setuid privileges, allowing users to gain privileges.
CVE-2008-4638

Composite: application running with high privileges (CWE-250) allows user to specify a restricted file to process, which generates a parsing error that leaks the contents of the file (CWE-209).
CVE-2008-0162

Program does not drop privileges before calling another program, allowing code execution.
CVE-2008-0368

setuid root program allows creation of arbitrary files through command line argument.
CVE-2007-3931

Installation script installs some programs as setuid when they shouldn't be.
CVE-2020-3812

mail program runs as root but does not drop its privileges before attempting to access a file. Attacker can use a symlink from their home directory to a directory only readable by root, then determine whether the file exists based on the response.

Como os atacantes a exploram

Trajeto do atacante passo a passo

1
This code temporarily raises the program's privileges to allow creation of a new user folder.
2
While the program only raises its privilege level to create the folder and immediately lowers it again, if the call to os.mkdir() throws an exception, the call to lowerPrivileges() will not occur. As a result, the program is indefinitely operating in a raised privilege state, possibly allowing further exploitation to occur.
3
The following code calls chroot() to restrict the application to a subset of the filesystem below APP_HOME in order to prevent an attacker from using the program to gain unauthorized access to files located elsewhere. The code then opens a file specified by the user and processes the contents of the file.
4
Constraining the process inside the application's home directory before opening any files is a valuable security measure. However, the absence of a call to setuid() with some non-zero value means the application is continuing to operate with unnecessary root privileges. Any successful exploit carried out by an attacker against the application can now result in a privilege escalation attack because any malicious operations will be performed with the privileges of the superuser. If the application drops to the privilege level of a non-root user, the potential for damage is substantially reduced.
5
This application intends to use a user's location to determine the timezone the user is in:

Exemplo de código vulnerável

Vulnerable Python

This code temporarily raises the program's privileges to allow creation of a new user folder.

Vulnerável Python

def makeNewUserDir(username):
  		if invalidUsername(username):
```
#avoid CWE-22 and CWE-78* 
  				print('Usernames cannot contain invalid characters')
  				return False
  		try:
  		```
  			raisePrivileges()
  			os.mkdir('/home/' + username)
  			lowerPrivileges()
  		except OSError:
  			print('Unable to create new user directory for user:' + username)
  			return False
  		return True

Exemplo de código seguro

Secure pseudo

Seguro 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.

Lista de verificação de prevenção

How to prevent CWE-250

Architecture and Design / Operation Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.
Architecture and Design Identify the functionality that requires additional privileges, such as access to privileged operating system resources. Wrap and centralize this functionality if possible, and isolate the privileged code as much as possible from other code [REF-76]. Raise privileges as late as possible, and drop them as soon as possible to avoid CWE-271. Avoid weaknesses such as CWE-288 and CWE-420 by protecting all possible communication channels that could interact with the privileged code, such as a secondary socket that is only intended to be accessed by administrators.
Architecture and Design Identify the functionality that requires additional privileges, such as access to privileged operating system resources. Wrap and centralize this functionality if possible, and isolate the privileged code as much as possible from other code [REF-76]. Raise privileges as late as possible, and drop them as soon as possible to avoid CWE-271. Avoid weaknesses such as CWE-288 and CWE-420 by protecting all possible communication channels that could interact with the privileged code, such as a secondary socket that is only intended to be accessed by administrators.
Implementation Perform extensive input validation for any privileged code that must be exposed to the user and reject anything that does not fit your strict requirements.
Implementation When dropping privileges, ensure that they have been dropped successfully to avoid CWE-273. As protection mechanisms in the environment get stronger, privilege-dropping calls may fail even if it seems like they would always succeed.
Implementation If circumstances force you to run with extra privileges, then determine the minimum access level necessary. First identify the different permissions that the software and its users will need to perform their actions, such as file read and write permissions, network socket permissions, and so forth. Then explicitly allow those actions while denying all else [REF-76]. Perform extensive input validation and canonicalization to minimize the chances of introducing a separate vulnerability. This mitigation is much more prone to error than dropping the privileges in the first place.
Operation / System Configuration Ensure that the software runs properly under the United States Government Configuration Baseline (USGCB) [REF-199] or an equivalent hardening configuration guide, which many organizations use to limit the attack surface and potential risk of deployed software.

Sinais de deteção

How to detect CWE-250

Manual Analysis

This weakness can be detected using 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.

Black Box

Use monitoring tools that examine the software's process as it interacts with the operating system and the network. This technique is useful in cases when source code is unavailable, if the software was not developed by you, or if you want to verify that the build phase did not introduce any new weaknesses. Examples include debuggers that directly attach to the running process; system-call tracing utilities such as truss (Solaris) and strace (Linux); system activity monitors such as FileMon, RegMon, Process Monitor, and other Sysinternals utilities (Windows); and sniffers and protocol analyzers that monitor network traffic. Attach the monitor to the process and perform a login. Look for library functions and system calls that indicate when privileges are being raised or dropped. Look for accesses of resources that are restricted to normal users.

Automated Static Analysis - Binary or Bytecode High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Compare binary / bytecode to application permission manifest ``` Cost effective for partial coverage: ``` Bytecode Weakness Analysis - including disassembler + source code weakness analysis Binary Weakness Analysis - including disassembler + source code weakness analysis

Manual Static Analysis - Binary or Bytecode SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Dynamic Analysis with Automated Results Interpretation SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Host-based Vulnerability Scanners - Examine configuration for flaws, verifying that audit mechanisms work, ensure host configuration meets certain predefined criteria

Dynamic Analysis with Manual Results Interpretation SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Host Application Interface Scanner

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-250 e abre um PR de correção em menos de 60 segundos.

O Codex Remedium analisa cada commit, identifica esta fraqueza exata e entrega um pull request pronto para revisão com o patch. Sem tickets. Sem transferências.

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Perguntas frequentes

Frequently asked questions

O que é o CWE-250?

Qual a gravidade do CWE-250?

A MITRE classifica a probabilidade de exploração como Média — a exploração é realista mas normalmente requer condições específicas.

Que linguagens ou plataformas são afetadas pelo CWE-250?

MITRE lists the following affected platforms: Mobile.

Como posso prevenir o CWE-250?

Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations. Identify the functionality that requires…

Como é que o Plexicus deteta e corrige o CWE-250?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-250 em cada commit. Quando é encontrada uma correspondência, o nosso agente Codex Remedium abre um PR de correção com o código corrigido, testes e um resumo de uma linha para o revisor.

Onde posso saber mais sobre o CWE-250?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/250.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-250

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Privilege Defined With Unsafe Actions

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Privilege Chaining

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CWE-270 Irmão

Privilege Context Switching Error

This vulnerability occurs when an application fails to properly manage user permissions while moving between different security contexts,…

CWE-271 Irmão

Privilege Dropping / Lowering Errors

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a…

CWE-274 Irmão

Improper Handling of Insufficient Privileges

This vulnerability occurs when an application fails to properly manage situations where it lacks the necessary permissions to execute an…

CWE-648 Irmão

Incorrect Use of Privileged APIs

This vulnerability occurs when software incorrectly uses functions that require special permissions. Attackers can exploit these mistakes…

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