CVE-2026-63622 in Red Hat
Summary
by MITRE • 08/11/2026
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.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability exists within the libvirt virtualization management library and represents a critical privilege escalation flaw that undermines the security boundaries of virtualized environments. The issue stems from improper handling of symbolic links in the virFileChownFiles() function, which operates at the system level while processing files owned by the swtpm user. When a local attacker executes a process running under the confined swtpm user context, they can manipulate the state directory to create malicious symbolic links that exploit this vulnerability.
The technical mechanism involves a classic symlink race condition where the vulnerable function follows symbolic links without proper validation or restriction mechanisms. The swtpm service typically operates in a restricted environment with limited privileges, yet the flaw allows an attacker to manipulate file ownership through a carefully crafted symlink attack. This occurs because libvirt's daemon process, running at root level, processes files in the swtpm state directory and follows symbolic links without implementing proper path validation or sandboxing controls.
The operational impact of this vulnerability is severe as it enables attackers to escalate privileges from the confined swtpm user to full root-level file ownership control. This means an attacker who gains access to execute code as the swtpm user can manipulate arbitrary files on the system, potentially gaining access to sensitive data, modifying critical system files, or establishing persistent access. The attack vector requires local access and execution privileges within the swtpm sandbox but provides a significant escalation path that undermines the principle of least privilege.
From a cybersecurity perspective, this vulnerability aligns with CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions, and demonstrates weaknesses in proper privilege separation and file system access controls. The flaw also maps to ATT&CK technique T1068, privilege escalation through local exploitation, and T1548.001, which covers abuse of system privileges for persistence. Organizations running libvirt-based virtualization environments are particularly vulnerable, as this affects systems where swtpm is used for TPM emulation in virtual machines.
The mitigation strategy requires immediate patching of the libvirt library to implement proper symlink validation and prevent the daemon from following symbolic links when processing files in restricted directories. Additionally, system administrators should review and harden the swtpm configuration to minimize privilege escalation paths, implement proper file access controls, and ensure that the state directory permissions are properly configured to prevent unauthorized symbolic link creation. Monitoring for suspicious file ownership changes and implementing process isolation measures can provide additional defense-in-depth layers against exploitation attempts.