UNIX Hard Link
Incomplete Variant
Structure: Simple
Description
The product, 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 product to operate on unauthorized files.
Failure 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.
Common Consequences 1
Scope: ConfidentialityIntegrity
Impact: Read Files or DirectoriesModify Files or Directories
Potential Mitigations 1
Phase: Architecture and Design
Strategy: 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.
Observed Examples 10
CVE-2001-1494Hard link attack, file overwrite; interesting because program checks against soft links
CVE-2002-0793Hard link and possibly symbolic link following vulnerabilities in embedded operating system allow local users to overwrite arbitrary files.
CVE-2003-0578Server creates hard links and unlinks files as root, which allows local users to gain privileges by deleting and overwriting arbitrary files.
CVE-1999-0783Operating 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-2004-1603Web hosting manager follows hard links, which allows local users to read or modify arbitrary files.
CVE-2004-1901Package listing system allows local users to overwrite arbitrary files via a hard link attack on the lockfiles.
CVE-2005-0342The Finder in Mac OS X and earlier allows local users to overwrite arbitrary files and gain privileges by creating a hard link from the .DS_Store file to an arbitrary file.
CVE-2005-1111Hard link race condition
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.
CVE-2003-1366setuid root tool allows attackers to read secret data by replacing a temp file with a hard link to a sensitive file
References 1
The Art of Software Security Assessment
Mark Dowd, John McDonald, and Justin Schuh
Addison Wesley
2006
ID: REF-62
Applicable Platforms
Languages:
Not Language-Specific : Undetermined
Modes of Introduction
Implementation
Functional Areas
- File Processing
Affected Resources
- File or Directory
Related Weaknesses
Taxonomy Mapping
- PLOVER
- CERT C Secure Coding
- Software Fault Patterns