CVE-2026-63622

A flaw was found in libvirt. A local attacker, specifically a process running as the confined swtpm user, could exploit a symlink-following vulnerability in the virFileChownFiles() function. By planting a symbolic link within the swtpm state directory, the attacker could trick the root-level libvirt daemon into changing the ownership of an arbitrary file to the swtpm user. This allows for privilege escalation from the swtpm sandbox to root-level file ownership control.

This vulnerability is rated as having an Important severity because a compromise of the unprivileged swtpm service can allow an attacker to bypass isolation boundaries and seize control of arbitrary host files with root privileges. In standard Red Hat Enterprise Linux deployments, virtualization hosts are only exposed if virtual machines are explicitly configured to use emulated TPM (swtpm) devices. Although triggering the condition requires local privileges under the dedicated tss account, successful exploitation circumvents the daemon sandbox, resulting in full host compromise.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

If virtual Trusted Platform Module (vTPM) functionality is not required, remove the <tpm> device definition from the domain XML configuration to prevent the vulnerable code path from being reached.

To check if a domain uses vTPM:

virsh dumpxml <domain> | grep -A5 '<tpm'

To remove it, edit the domain XML and delete the <tpm> block. This prevents libvirt from spawning swtpm processes and from calling virFileChownFiles() on the swtpm state directory during domain startup. Domains that require vTPM for guest OS functionality cannot use this mitigation and should prioritize applying the upstream fix.