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CWE-61

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CWE-61

UNIX Symbolic Link (Symlink) Following

Compound
Incomplete

Description

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.

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.

Common Consequences

Scope

Confidentiality
Integrity

Impact

Read Files or Directories, Modify Files or Directories

Potential Mitigations

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.

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.

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.

+3 more examples

Applicable Platforms

Not Language-Specific

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