Local Privilege Escalation in libvirt via Symlink Following (CVE-2026-63622)

A vulnerability identified as CVE-2026-63622 exists within the libvirt management library, specifically involving the virFileChownFiles() function. The flaw enables a local attacker, operating under the constrained swtpm user context, to perform unauthorized file ownership changes. By creating malicious symbolic links within the swtpm state directory, an attacker can influence the libvirt daemon - which runs with root privileges - to perform a chown operation on arbitrary files on the host system. This mechanism effectively breaks the sandbox isolation, allowing the swtpm process to gain ownership of system files, thereby facilitating privilege escalation to root-level file access. This vulnerability is significant for environments leveraging virtual machine TPM emulation.

Impact

Successful exploitation allows a low-privileged swtpm process to gain ownership over arbitrary files on the host filesystem. This impact is critical in multi-tenant environments or systems relying on libvirt for virtualization security, as it provides a pathway for the attacker to manipulate security-sensitive files, bypass access controls, or escalate privileges to full root access depending on the target file selected for ownership transition.

Recommendation

• Apply vendor-supplied patches for the libvirt library immediately to address CVE-2026-63622.
• Audit the swtpm state directory locations on virtualization hosts for unusual symbolic link creations.
• Implement stricter SELinux or AppArmor profiles for the swtpm process to restrict file system access outside of designated state directories.
• Monitor for unexpected calls to chown or fchown initiated by the libvirtd process.