Critical [CVE-2026-16658] proxmox_pct_remote shel injection via unquoted pct exec command allows
This critical-severity Red Hat Linux advisory covers CVE-2026-16658.
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Summary
A flaw was found in the community.proxmox Ansible collection's proxmox_pct_remote connection plugin. The _build_pct_command() method constructs a pct exec command string using unquoted string concatenation and passes it to the Proxmox host's shell via Paramiko.
Shell metacharacters in the command (such as >, |,;, &&, or $()) are interpreted on the host instead of inside the target LXC container, allowing commands intended for an unprivileged container to execute on the hypervisor host as root. This constitutes a container-to-host trust boundary crossing.
The put_file and fetch_file methods in the same plugin correctly use shell quoting, indicating this is an oversight on the exec path. while CVSS has a score of 9.9, the impact is rated as IMPORTANT for Red Hat assessment due to deployment-dependent privilege model determining risks. 1.
In most Proxmox deployments, the Ansible SSH user already has root/sudo on the host (to run pct). In that case, the shell injection does not escalate privileges — it changes WHERE commands execute (host vs container) but the operator already has host access.
2. In multi-tenant or delegated management models where Ansible operators have container access but NOT host access, this IS a genuine privilege escalation / container escape.
3.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 55 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 55 minutes ago·verify at source
Mitigation checklist
- - Avoid using shell metacharacters (>, <, |, ;, &&, $()) in tasks targeting LXC containers via the proxmox_pct_remote connection plugin. Use the ansible.builtin.copy or ansible.builtin.template modules instead of raw/shell tasks for file operations. - Audit recent Ansible task logs for any tasks run via proxmox_pct_remote that contained shell metacharacters — these may have executed on the Proxmox host instead of the container. Check for unintended file modifications on the host. - As a temporary workaround, manually quote commands in tasks: ansible.builtin.raw: "pct exec {{ vmid }} -- sh -c '{{ cmd | quote }}'" (This bypasses the connection plugin's command construction.)
Official advisory · high-confidence parse· fetched 55 minutes ago·verify at source
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