rsync before 3.5.0 contains a symlink race condition vulnerability that allows local attackers to cause rsync to apply arbitrary ACLs or extended attributes to unintended files by substituting a symlink at a predictable destination path between the file write and the subsequent acl_set_file() or lsetxattr() call. Attackers can exploit this timing window to redirect ACL and xattr application through a crafted symlink to files outside the intended destination tree, potentially granting elevated permissions and enabling local privilege escalation.
Weakness
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
Potential Mitigations
- 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.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/132.html
- https://cwe.mitre.org/data/definitions/17.html
- https://cwe.mitre.org/data/definitions/35.html
- https://cwe.mitre.org/data/definitions/76.html