CWE-59 Base Rascunho Medium likelihood

Improper Link Resolution Before File Access ('Link Following')

This vulnerability occurs when an application uses a filename to access a file but fails to properly check if that name points to a symbolic link, shortcut, or junction. This allows an attacker to…

Definição

What is CWE-59?

This vulnerability occurs when an application uses a filename to access a file but fails to properly check if that name points to a symbolic link, shortcut, or junction. This allows an attacker to manipulate the link's target, causing the application to read or write to an unintended, potentially sensitive location.
At its core, this is a path traversal issue enabled by symbolic links. When a program doesn't verify that a file is a regular file and not a link, an attacker can create a link that points outside the intended directory—like a system file or another user's data. The application then blindly follows this link, leading to unauthorized access, data corruption, or a denial of service. To prevent this, developers must explicitly resolve symbolic links before performing file operations. This involves using system calls or functions that return the canonical path of a file, checking the file's type, and implementing proper access controls. Always assume filenames provided by users or external sources are untrusted and validate the final resolved path against a safe allowlist.
Impacto no mundo real

Real-world CVEs caused by CWE-59

  • CVE-1999-1386

    Some versions of Perl follow symbolic links when running with the -e option, which allows local users to overwrite arbitrary files via a symlink attack.

  • CVE-2000-1178

    Text editor follows symbolic links when creating a rescue copy during an abnormal exit, which allows local users to overwrite the files of other users.

  • CVE-2004-0217

    Antivirus update allows local users to create or append to arbitrary files via a symlink attack on a logfile.

  • CVE-2003-0517

    Symlink attack allows local users to overwrite files.

  • CVE-2004-0689

    Window manager does not properly handle when certain symbolic links point to "stale" locations, which could allow local users to create or truncate arbitrary files.

  • CVE-2005-1879

    Second-order symlink vulnerabilities

  • CVE-2005-1880

    Second-order symlink vulnerabilities

  • CVE-2005-1916

    Symlink in Python program

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    Identificar um caminho de código que trata input não confiável sem validação.

  2. 2

    Criar um payload que explora o comportamento inseguro — injeção, traversal, overflow ou abuso de lógica.

  3. 3

    Entregar o payload através de um pedido normal e observar a reação da aplicação.

  4. 4

    Iterar até que a resposta exponha dados, execute código do atacante ou escale privilégios.

Exemplo de código vulnerável

Vulnerable pseudo

A MITRE não publicou um exemplo de código para este CWE. O padrão abaixo é ilustrativo — consulte os Recursos para referências canónicas.

Vulnerável pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
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-59

  • Architecture and Design Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
Sinais de deteção

How to detect CWE-59

Automated Static Analysis - Binary or Bytecode SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Bytecode 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: ``` Web Application Scanner Web Services Scanner Database Scanners

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: ``` Fuzz Tester Framework-based Fuzzer

Manual Static Analysis - Source Code High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Focused Manual Spotcheck - Focused manual analysis of source Manual Source Code Review (not inspections)

Automated Static Analysis - Source Code SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Source code Weakness Analyzer Context-configured Source Code Weakness Analyzer

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-59 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-59?

This vulnerability occurs when an application uses a filename to access a file but fails to properly check if that name points to a symbolic link, shortcut, or junction. This allows an attacker to manipulate the link's target, causing the application to read or write to an unintended, potentially sensitive location.

Qual a gravidade do CWE-59?

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-59?

MITRE lists the following affected platforms: Windows, Unix.

Como posso prevenir o CWE-59?

Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Como é que o Plexicus deteta e corrige o CWE-59?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-59 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-59?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/59.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-59

CWE-706 Pai

Use of Incorrectly-Resolved Name or Reference

This vulnerability occurs when software uses a name, path, or reference to access a resource, but that identifier points to something…

CWE-178 Irmão

Improper Handling of Case Sensitivity

This vulnerability occurs when software fails to consistently handle uppercase and lowercase letters when checking or accessing resources,…

CWE-22 Irmão

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

This vulnerability occurs when an application builds a file path using user input but fails to properly validate it, allowing an attacker…

CWE-386 Irmão

Symbolic Name not Mapping to Correct Object

This vulnerability occurs when a program uses a fixed symbolic name (like a constant or identifier) to refer to an object, but that name…

CWE-41 Irmão

Improper Resolution of Path Equivalence

This vulnerability occurs when an application fails to properly handle different text representations that refer to the same file or…

CWE-66 Irmão

Improper Handling of File Names that Identify Virtual Resources

This vulnerability occurs when software incorrectly processes a filename that points to a 'virtual' resource—like a device, pipe, or…

CWE-827 Irmão

Improper Control of Document Type Definition

This vulnerability occurs when an application fails to properly restrict which Document Type Definitions (DTDs) can be referenced during…

CWE-98 Irmão

Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion')

This vulnerability occurs when a PHP application uses unvalidated or insufficiently restricted user input directly within file inclusion…

CWE-1386 Filho

Insecure Operation on Windows Junction / Mount Point

This vulnerability occurs when a Windows application opens a file or directory without properly validating that the path is not a symbolic…

Recursos

Further reading

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