A malicious application may be able to overwrite arbitrary files. This issue is fixed in macOS Big Sur 11.4, Security Update 2021-004 Mojave. An issue with path validation logic for hardlinks was addressed with improved path sanitization.
https://support.apple.com/en-us/HT212531
https://support.apple.com/en-us/HT212529
Source: Mitre, NVD
Published: 2021-09-08
Updated: 2021-09-22
Base Score: 2.1
Vector: CVSS2#AV:L/AC:L/Au:N/C:N/I:P/A:N
Severity: Low
Base Score: 5.5
Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Severity: Medium