Home Assistant Core before 2026.6.0 contains a path traversal vulnerability that allows unauthenticated attackers to write arbitrary files to any directory on the host filesystem by uploading a crafted backup archive during the initial onboarding window. Attackers can manipulate the 'name' field inside the uploaded archive's backup.json to supply an absolute path, causing pathlib.Path.__truediv__ to discard the configured backup directory prefix and write attacker-controlled content to arbitrary locations, with full filesystem access when the process runs as root.
CVSS Details
- CVSS 4.0 Base Score: 9 (CRITICAL)
- CVSS 4.0 Vector: (CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:H/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X)
- CVSS 3.1 Base Score: 9.3
- CVSS 3.1 Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:L)
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