CWE

CWE-62 – UNIX Hard Link

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Description

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 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.

Modes of Introduction:

– Implementation

 

 

Related Weaknesses

CWE-59

 

Consequences

Confidentiality, Integrity: Read Files or Directories, Modify Files or Directories

 

Potential Mitigations

Phase: Architecture and Design

Description: 

CVE References

  • 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-2005-0342
    • The 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.