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.
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-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.