CWE-61 Detalhe

CWE-61

UNIX Symbolic Link (Symlink) Following
Alta
Incomplete
2006-07-19
00h00 +00:00
2025-12-11
00h00 +00:00
CWE Mitre.org
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Nome: UNIX Symbolic Link (Symlink) Following

The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

Descrição CWE

A product that allows UNIX symbolic links (symlink) as part of paths whether in internal code or through user input can allow an attacker to spoof the symbolic link and traverse the file system to unintended locations or access arbitrary files. The symbolic link can permit an attacker to read/write/corrupt a file that they originally did not have permissions to access.

Informações Gerais

Modos de Introdução

Implementation : These are typically reported for temporary files or privileged programs.

Plataformas Aplicáveis

Linguagem

Class: Not Language-Specific (Undetermined)

Consequências Comuns

Escopo Impacto Probabilidade
Confidentiality
Integrity		Read Files or Directories, Modify Files or Directories

Exemplos Observados

Referências Descrição

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

Possible interesting example

CVE-2005-1879

Second-order symlink vulnerabilities

CVE-2005-1880

Second-order symlink vulnerabilities

CVE-2005-1916

Symlink in Python program

CVE-2000-0972

Setuid product allows file reading by replacing a file being edited with a symlink to the targeted file, leaking the result in error messages when parsing fails.

CVE-2005-0824

Signal causes a dump that follows symlinks.

CVE-2015-3629

A Libcontainer used in Docker Engine allows local users to escape containerization and write to an arbitrary file on the host system via a symlink attack in an image when respawning a container.

CVE-2020-26277

In a MySQL database deployment tool, users may craft a maliciously packaged tarball that contains symlinks to files external to the target and once unpacked, will execute.

CVE-2021-21272

"Zip Slip" vulnerability in Go-based Open Container Initiative (OCI) registries product allows writing arbitrary files outside intended directory via symbolic links or hard links in a gzipped tarball.

Mitigações Potenciais

Phases : Implementation
Symbolic link attacks often occur when a program creates a tmp directory that stores files/links. Access to the directory should be restricted to the program as to prevent attackers from manipulating the files.
Phases : Architecture and Design

Métodos de Detecção

Automated Static Analysis

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.)

Notas de Mapeamento de Vulnerabilidade

Justificativa : This is a well-known Composite of multiple weaknesses that must all occur simultaneously, although it is attack-oriented in nature.
Comentário : While attack-oriented composites are supported in CWE, they have not been a focus of research. There is a chance that future research or CWE scope clarifications will change or deprecate them. Perform root-cause analysis to determine which weaknesses allow symlink following to occur, and map to those weaknesses. For example, predictable file names might be intended functionality, but creation in a directory with insecure permissions might not.

Padrões de Ataque Relacionados

CAPEC-ID Nome do Padrão de Ataque
CAPEC-27 Leveraging Race Conditions via Symbolic Links
This attack leverages the use of symbolic links (Symlinks) in order to write to sensitive files. An attacker can create a Symlink link to a target file not otherwise accessible to them. When the privileged program tries to create a temporary file with the same name as the Symlink link, it will actually write to the target file pointed to by the attackers' Symlink link. If the attacker can insert malicious content in the temporary file they will be writing to the sensitive file by using the Symlink. The race occurs because the system checks if the temporary file exists, then creates the file. The attacker would typically create the Symlink during the interval between the check and the creation of the temporary file.

Notas


Referências

REF-493

Second-Order Symlink Vulnerabilities
Steve Christey.
https://seclists.org/bugtraq/2005/Jun/44

REF-494

Crafting Symlinks for Fun and Profit
Shaun Colley.
https://web.archive.org/web/20040502153535/http://www.infosecwriters.com/texts.php?op=display&id=159

REF-62

The Art of Software Security Assessment
Mark Dowd, John McDonald, Justin Schuh.

Submissão

Nome Organização Data Data de lançamento Version
PLOVER 2006-07-19 +00:00 2006-07-19 +00:00 Draft 3

Modificações

Nome Organização Data Comentário
Eric Dalci Cigital 2008-07-01 +00:00 updated Time_of_Introduction
CWE Content Team MITRE 2008-09-08 +00:00 updated Relationships, Observed_Example, Other_Notes, Research_Gaps, Taxonomy_Mappings, Weakness_Ordinalities
CWE Content Team MITRE 2008-10-14 +00:00 updated Description
CWE Content Team MITRE 2009-07-27 +00:00 updated Observed_Examples
CWE Content Team MITRE 2011-06-01 +00:00 updated Common_Consequences
CWE Content Team MITRE 2012-05-11 +00:00 updated Observed_Examples, References
CWE Content Team MITRE 2012-10-30 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2014-06-23 +00:00 updated Modes_of_Introduction, Other_Notes
CWE Content Team MITRE 2017-11-08 +00:00 updated Applicable_Platforms, Causal_Nature, Likelihood_of_Exploit, References, Relationships
CWE Content Team MITRE 2020-02-24 +00:00 updated Relationships
CWE Content Team MITRE 2022-04-28 +00:00 updated Research_Gaps
CWE Content Team MITRE 2022-10-13 +00:00 updated Observed_Examples
CWE Content Team MITRE 2023-01-31 +00:00 updated Description
CWE Content Team MITRE 2023-04-27 +00:00 updated References, Relationships
CWE Content Team MITRE 2023-06-29 +00:00 updated Mapping_Notes
CWE Content Team MITRE 2025-09-09 +00:00 updated Affected_Resources, Functional_Areas, References
CWE Content Team MITRE 2025-12-11 +00:00 updated Detection_Factors, Relationships
As informações apresentadas no CVE Find originam-se de várias fontes de referência cuidadosamente selecionadas. Os dados CVE são fornecidos pela MITRE Corporation e pelo National Vulnerability Database (NVD). O catálogo de Vulnerabilidades Conhecidas Exploradas (KEV) é proveniente da Cybersecurity and Infrastructure Security Agency (CISA), enquanto as pontuações EPSS vêm do FIRST.org. Além disso, os dados sobre fraquezas de software (CWE) e padrões de ataque comuns (CAPEC) são mantidos pela MITRE Corporation, e as informações sobre configurações de hardware e software (CPE) são fornecidas pelo NVD.