UNIX Hard Link
|ID: 62||Date: (C)2012-05-14 (M)2012-11-08|
|Type: weakness||Status: INCOMPLETE|
|Abstraction Type: Variant|
The software, when opening a file or directory, does not
sufficiently account for when the name is associated with a hard link to a
target that is outside of the intended control sphere. This could allow an
attacker to cause the software to operate on unauthorized
Extended DescriptionFailure for a system to check for hard links can result in vulnerability
to different types of attacks. For example, an attacker can escalate their
privileges if a file used by a privileged program is replaced with a hard
link to a sensitive file (e.g. /etc/passwd). When the process opens the
file, the attacker can assume the privileges of that process.
Applicable PlatformsLanguage Class: AllOperating System Class: UNIX
Time Of Introduction
|ConfidentialityIntegrity ||Read files or
directoriesModify files or
directories || |
|Architecture and Design ||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. || || |
|CWE-62 ChildOf CWE-893 ||Category ||CWE-888 || |
- CVE-2001-1494 : Hard link attack, file overwrite; interesting because program checks against soft links
- CVE-2002-0793 : Hard link and possibly symbolic link following vulnerabilities in embedded operating system allow local users to overwrite arbitrary files.
- CVE-2003-0578 : Server creates hard links and unlinks files as root, which allows local users to gain privileges by deleting and overwriting arbitrary files.
- CVE-1999-0783 : Operating system allows local users to conduct a denial of service by creating a hard link from a device special file to a file on an NFS file system.
- CVE-2004-1603 : Web hosting manager follows hard links, which allows local users to read or modify arbitrary files.
- CVE-2004-1901 : Package listing system allows local users to overwrite arbitrary files via a hard link attack on the lockfiles.
- CVE-2005-1111 : Hard link race condition
- ASA-0001 : OpenBSD chpass/chfn/chsh file content leak
For more examples, refer to CVE relations in the bottom box.
White Box Definitions None
Black Box Definitions None
|PLOVER || ||UNIX hard link || |
|CERT C Secure Coding ||FIO05-C ||Identify files using multiple file
attributes || |
|CERT C++ Secure Coding ||FIO05-CPP ||Identify files using multiple file
attributes || |
- Mark Dowd John McDonald Justin Schuh .The Art of Software Security Assessment 1st Edition. Addison Wesley. Section:'Chapter 9, "Hard Links", Page 518.'. Published on 2006.