The Ubuntu-specific language helper scripts (save-to-pam-env, update-langlist) shipped with accountsservice before 23.13.9-8ubuntu7 treat the user-controlled LANGUAGE entry in ~/.pam_environment as trusted input. The value is interpolated unescaped into a GNU sed replacement expression, allowing an attacker to inject a sed 'e' flag and arbitrary shell commands that execute with the privileges of the AccountsService helper process (real UID 0) via the SetLanguage D-Bus method.
Attack Parameters
Attack Vector
Local
Requires local access
Attack Complexity
Low
Easy to exploit
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service
CVSS Vector v3.1