Executive brief
Qubes OS uses qvm-copy-to-vm to securely copy files between the trusted Dom0 management domain and less-trusted virtual machines. A flaw in error message handling allows a compromised VM to inject shell commands that execute with Dom0 privileges, fully compromising the entire Qubes OS system. This affects any user who copies files from Dom0 to an untrusted VM.
Technical details
The vulnerability is a command injection flaw in the qvm-copy-to-vm file transfer tool's error reporting mechanism. When file transfer fails, the target VM reports an error code and filename back to Dom0, which sanitizes only non-ASCII characters and quotes but leaves shell metacharacters intact. The Dom0 error handler then passes this unsanitized filename to system() call, which invokes a shell to display a dialog—allowing arbitrary command execution with Dom0 privileges. The attack requires an attacker to control a target VM that receives a copy request, but does not require prior compromise of Dom0 itself. The vulnerability affects all Qubes OS versions and is fixed in qubes-core-dom0-linux version 4.3.22 or later; the VM-side variant is unaffected because it uses execl() instead of system().
Affected products
- Qubes OS before 4.3.22
Timeline
- 2026-08-29: disclosed
- 2026-08-28: patched: qubes-core-dom0-linux version 4.3.22