# CVE-2026-93834: Qemu-kvm: 9pfs: use-after-free race in tlcreate/twalk allows vm guest escape

Status: published. Published: 2026-09-25. Updated: 2026-11-05.

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.

## Remediation

- 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: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (qemu-kvm): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (qemu-kvm): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (qemu-kvm): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (qemu-kvm-ma): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (virt-devel:rhel/qemu-kvm): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (virt:rhel/qemu-kvm): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (qemu-kvm): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux for NVIDIA 26 (qemu-kvm): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-8): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 5 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenStack Platform 13 (Queens) (qemu-kvm-rhev): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: 0.40% as of 2026-11-04; percentile 34.89%

- SSVC: exploitation poc; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-416

## Exploit evidence

- exploit: https://gitlab.com/qemu-project/qemu/-/work_items/4491 (ADP: CISA-ADP)

## References

- https://access.redhat.com/security/cve/CVE-2026-93834 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2537939 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://gitlab.com/qemu-project/qemu/-/work_items/4491 (CNA: redhat)

- https://gitlab.com/qemu-project/qemu/-/work_items/4491 (ADP: CISA-ADP; exploit)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-93834; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-93834; retrieved 2026-11-05; source updated Not reported

Revision: f5314725cfe63e186ff5e0585b08d14c371e625bf0880d83d17bb69f97609461

Canonical: https://y2.dev/cve/CVE-2026-93834

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