CVE-2026-93834
Qemu-kvm: 9pfs: use-after-free race in tlcreate/twalk allows vm guest escape
A use-after-free vulnerability was found in QEMU's 9pfs subsystem. A race condition between the main thread and a worker thread when processing concurrent Tlcreate and Twalk requests allows a malicious guest user to craft a fid path containing stale heap data, bypassing directory traversal restrictions and escaping the shared directory boundary. This can lead to arbitrary host file read/write and code execution (VM escape) as the QEMU process user.
Fixes and workarounds
Workaround
Do not configure 9pfs/VirtFS filesystem sharing (-fsdev, -virtfs) on affected QEMU instances. If host-guest file sharing is required, use virtio-fs (virtiofsd) as an alternative, which does not use the vulnerable 9pfs code path.
Source: CNA: redhatAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| Red Hat Enterprise Linux 10 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux 6 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: unaffected |
CNA: redhat |
| Red Hat Enterprise Linux 7 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: unaffected |
CNA: redhat |
| Red Hat Enterprise Linux 7 Red Hat qemu-kvm-ma
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: unaffected |
CNA: redhat |
| Red Hat Enterprise Linux 8 Red Hat virt-devel:rhel/qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux 8 Red Hat virt:rhel/qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux 9 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat Enterprise Linux for NVIDIA 26 Red Hat qemu-kvm
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: unknown |
CNA: redhat |
| Red Hat OpenShift Container Platform 4 Red Hat openshift/ose-rhel-coreos-8
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat OpenShift Container Platform 4 Red Hat openshift/ose-rhel-coreos-9
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat OpenShift Container Platform 5 Red Hat openshift/ose-rhel-coreos-9
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: affected |
CNA: redhat |
| Red Hat OpenStack Platform 13 (Queens) Red Hat qemu-kvm-rhev
https://access.redhat.com/downloads/content/package-browser/ |
Range not reported
Other versions: unaffected |
CNA: redhat |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 8.8 high |
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H | CNA: redhat |
Exploit evidence
- https://gitlab.com/qemu-project/qemu/-/work_items/4491
exploit · ADP: CISA-ADP
References
- https://access.redhat.com/security/cve/CVE-2026-93834CNA: redhat · vdb-entry, x_refsource_REDHAT
- https://bugzilla.redhat.com/show_bug.cgi?id=2537939CNA: redhat · issue-tracking, x_refsource_REDHAT
- https://gitlab.com/qemu-project/qemu/-/work_items/4491CNA: redhat
- https://gitlab.com/qemu-project/qemu/-/work_items/4491ADP: CISA-ADP · exploit
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