CWE-61 UNIX符号链接跟随

UNIX Symbolic Link (Symlink) Following

结构: Composite

Abstraction: Compound

状态: Incomplete

被利用可能性: High

基本描述

The software, 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 software to operate on unauthorized files.

扩展描述

A software system 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.

相关缺陷

• cwe_Nature: ChildOf cwe_CWE_ID: 59 cwe_View_ID: 1000 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 59 cwe_View_ID: 699 cwe_Ordinal: Primary

• cwe_Nature: Requires cwe_CWE_ID: 362 cwe_View_ID: 1000

• cwe_Nature: Requires cwe_CWE_ID: 340 cwe_View_ID: 1000

• cwe_Nature: Requires cwe_CWE_ID: 216 cwe_View_ID: 1000

• cwe_Nature: Requires cwe_CWE_ID: 386 cwe_View_ID: 1000

• cwe_Nature: Requires cwe_CWE_ID: 732 cwe_View_ID: 1000

适用平台

Language: {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}

常见的影响

范围	影响	注释
['Confidentiality', 'Integrity']	['Read Files or Directories', 'Modify Files or Directories']

可能的缓解方案

Implementation

策略:

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.

MIT-48.1 Architecture and Design

策略: Separation of Privilege

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.

分析过的案例

标识	说明	链接
CVE-1999-1386	Some versions of Perl follows symbolic links when running with the -e option, which allows local users to overwrite arbitrary files via a symlink attack.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-1999-1386
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.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2000-1178
CVE-2004-0217	Antivirus update allows local users to create or append to arbitrary files via a symlink attack on a logfile.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-0217
CVE-2003-0517	Symlink attack allows local users to overwrite files.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2003-0517
CVE-2004-0689	Possible interesting example	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-0689
CVE-2005-1879	Second-order symlink vulnerabilities	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-1879
CVE-2005-1880	Second-order symlink vulnerabilities	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-1880
CVE-2005-1916	Symlink in Python program	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-1916
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.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2000-0972
CVE-2005-0824	Signal causes a dump that follows symlinks.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-0824

Notes

分类映射

映射的分类名	ImNode ID	Fit	Mapped Node Name
PLOVER			UNIX symbolic link following

相关攻击模式

• CAPEC-27

引用

• REF-493 Second-Order Symlink Vulnerabilities

• REF-494 Crafting Symlinks for Fun and Profit

• REF-62 The Art of Software Security Assessment

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