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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Compromise swtpm user execution
  2. Delivery
    Plant symlink in swtpm state directory
  3. Exploit
    Trigger libvirt daemon virFileChownFiles() call
  4. Execution
    Root daemon follows symlink, chowns target file
  5. Persist
    Attacker writes to now-owned sensitive file
  6. Impact
    Escalate to full root access

Vulnerability Assessment

Weakness
CWE
CWE-59
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V5 - File Handling Symlink resolution safety
Exploitation Conditions

Exploitation requires the attacker to already have code execution as the confined swtpm system user on the target host - this is not a remote or unauthenticated attack path. The vulnerability is only reachable on hosts where libvirt is configured to run virtual machines with software TPM emulation (vTPM), because the swtpm process and its associated state directory are only instantiated in that configuration; hosts running libvirt without vTPM-enabled VMs are not exposed. The attack is further limited to deployments where libvirtd runs as root (the standard RHEL configuration). Limiting factors: the attacker must first compromise the swtpm user through a separate vulnerability or misconfiguration; the swtpm user must have write access to the state directory (which is its normal operational condition); and SELinux in enforcing mode with a current targeted policy may independently constrain symlink traversal by libvirtd, though this has not been independently confirmed as a complete mitigation.
Impact

The CVSS 7.8 score with vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H is well-calibrated: the attack is local, requires only swtpm-level execution (PR:L), involves no complexity or race condition (AC:L), and results in full control over arbitrary file ownership (C:H/I:H/A:H). The S:U scope designation correctly reflects that the immediate impact is file ownership reassignment on the same host, not direct code execution - though ownership control over files like /etc/sudoers, /etc/shadow, or init scripts provides a credible path to full root compromise in a follow-on step. The vulnerability is not listed in the CISA KEV catalog, and no public proof-of-concept code has been identified, meaningopportunistic mass exploitation appears unlikely at this time. EPSS data was not provided, so probability-of-exploitation ranking cannot be derived from that source. The most realistic threat model is a chained attack: an initial swtpm binary compromise (e.g., via a separate bug) followed by this privilege escalation. Even a mid-sized municipal IT team in mielec operating a KVM hypervisor fleet with vTPM-enabled VMs should treat this as an urgent patch, since the attacker's pre-condition (swtpm user access) is a realistic intermediate step in VM breakout scenarios. The absence of active exploitation data should not be mistaken for low risk on systems where vTPM is in use.
Exploit ScenarioDerived

An attacker who has already obtained code execution as the swtpm confined user - for example through exploitation of a separate vulnerability in the swtpm binary or a misconfigured service - creates a symbolic link inside the swtpm state directory pointing to /etc/cron.d/backdoor. When libvirtd's root-level process next invokes virFileChownFiles() on that directory during a VM lifecycle event, it follows the symlink and transfers ownership of the target cron file to swtpm, after which the attacker writes an arbitrary cron job running as root. No public proof-of-concept has been identified, but the technique requires only standard filesystem operations available to the swtpm user.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 10, 2026

Privilege escalation in libvirt's virFileChownFiles() function allows a process confined to the swtpm system user to coerce the root-level libvirtd daemon into reassigning ownership of any arbitrary file on the host to the swtpm user. The attack exploits a symlink-following flaw (CWE-59) in directory traversal logic that runs with root privileges, affecting libvirt as packaged across Red Hat Enterprise Linux 6 through 10 and RHEL for Nvidia 26. No public exploit has been identified at time of analysis, but the attack complexity is low once swtpm-user execution is obtained.

RemediationAI

Apply the libvirt package update issued by Red Hat for the affected RHEL version, as documented at https://access.redhat.com/security/cve/CVE-2026-63622. The exact fixed package version is not confirmed in the available data and must be retrieved from the Red Hat advisory or errata for the specific RHEL release in use. As a compensating control where immediate patching is not feasible, disable vTPM support in all libvirt domain XML configurations - this prevents swtpm from being launched and eliminates the state directory that enables the attack, at the cost of removing hardware-rooted trust functionality from VMs that depend on it. On systems with SELinux in enforcing mode and an up-to-date targeted policy, symlink-following by libvirtd into swtpm directories may already be restricted by MAC policy; administrators should verify the active SELinux policy covers this path rather than assuming protection. Restricting write access to the swtpm state directory via filesystem ACLs is not a reliable mitigation since the swtpm user requires write access to that directory for normal operation.

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Technical ContextAI · show details

libvirt is the standard open-source virtualization management API used to control QEMU/KVM, Xen, and related hypervisors on Linux. The swtpm (Software TPM) component is a user-space emulator of a Trusted Platform Module, executed as a dedicated confined system user (swtpm) when virtual machines are configured with vTPM support. The vulnerable function, virFileChownFiles(), is invoked by libvirtd running as root to reassign ownership of files within the swtpm state directory. CWE-59 (Improper Link Resolution Before File Access - Link Following) is the root cause: the function does not validate that each filesystem entry in the directory is a regular file before calling chown, allowing a symbolic link planted by the attacker to redirect the privileged ownership change to an arbitrary path on the host filesystem. The CPE data confirms affected packages span cpe:2.3:a:red_hat:red_hat_enterprise_linux_6 through cpe:2.3:a:red_hat:red_hat_enterprise_linux_10 and cpe:2.3:a:red_hat:red_hat_enterprise_linux_for_nvidia_26, meaning the flaw is present in libvirt as distributed across all actively supported RHEL generations.

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Severity by source

Vendor (redhat) PRIMARY 7.8 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 7.8 HIGH

Local attack requires swtpm-user execution (PR:L, AV:L); symlink planting needs no complexity or timing (AC:L); arbitrary file chown yields full C/I/A impact.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
SUSE HIGH
Red Hat 7.8 HIGH

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionCVE.org

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.

Executive ViewAI

Why It Matters

CVE-2026-63622 is a privilege escalation vulnerability in libvirt affecting Red Hat Enterprise Linux versions 6 through 10 and RHEL for Nvidia 26, where unprivileged processes with swtpm user access can gain root-level control over arbitrary system files; no public exploit identified at time of analysis. This directly threatens system integrity and access controls across organizations deploying libvirt for virtualization or TPM management, with no vendor patch currently available. Organizations must prioritize compensating controls and continuous patch monitoring to reduce blast radius.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Implement the following interim mitigations: (1) enforce strict process-level access controls on swtpm execution using SELinux or AppArmor; (2) disable or remove the swtpm service entirely if TPM 2.0 support is not operationally required; (3) deploy real-time filesystem auditing and alerting on unexpected changes to critical system directories and file ownerships; (4) reduce attack surface by restricting local user and application access to affected libvirt hosts; (5) maintain continuous monitoring of Red Hat security channels and establish expedited testing and deployment procedures for emergency patches.

Threat Intelligence Overview

EPSS Score
0.1%
Top 97% exploitable
Prevalence
High
libvirt is the standard virtualization API across enterprise Linux and cloud infrastructure
Social Media
1
Sightings
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment Vendor CIRCL VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.1%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact
High
Technical Impact
Total

Priority Score

39
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +39
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Privilege Escalation HIGH

Privilege escalation occurs when an attacker leverages flaws in access control mechanisms to gain permissions beyond what they were originally granted.

Affected Products (CPE)CVE.org

cpe:2.3:a:red_hat:red_hat_enterprise_linux_10:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_6:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_7:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_8:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_9:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_for_nvidia_26:*:*:*:*:*:*:*:*

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Same weakness CWE-59 – Improper Link Resolution Before File Access

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Micro 5.3 Affected
SUSE Linux Enterprise Micro 5.4 Affected
SUSE Linux Enterprise Micro 5.5 Affected

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-63622 ADVISORY https://ubuntu.com/security/notices/USN-8833-1 ADVISORY https://vuldb.com/vuln/387933 REF https://access.redhat.com/errata/RHSA-2026:64773 REF https://access.redhat.com/errata/RHSA-2026:65515 REF https://access.redhat.com/errata/RHSA-2026:65516 REF https://access.redhat.com/errata/RHSA-2026:65803 REF https://access.redhat.com/errata/RHSA-2026:68513 REF https://access.redhat.com/errata/RHSA-2026:68594 REF https://access.redhat.com/errata/RHSA-2026:69114 REF https://access.redhat.com/errata/RHSA-2026:69131 REF https://access.redhat.com/errata/RHSA-2026:74424 REF https://access.redhat.com/errata/RHSA-2026:75583 REF https://access.redhat.com/security/cve/CVE-2026-63622 REF https://bugzilla.redhat.com/show_bug.cgi?id=2513065

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