Guest-to-host escape via 9pfs fid use-after-free
Published Sep 25, 2026 · Updated Sep 25, 2026
Use-after-free in Red Hat qemu-kvm 9pfs allows guest OS users to escape a shared directory and read or write host files through concurrent requests. Tlcreate frees a shared fid path on a worker thread while Twalk can still use that path, allowing reclaimed heap data to redirect traversal outside the export. Exploitation requires a configured virtio-9p share and guest access; demonstrated consequences include host code execution as the QEMU process user or a QEMU crash.
Summary
What happened
Use-after-free in Red Hat qemu-kvm 9pfs allows guest OS users to escape a shared directory and read or write host files through concurrent requests. Tlcreate frees a shared fid path on a worker thread while Twalk can still use that path, allowing reclaimed heap data to redirect traversal outside the export. Exploitation requires a configured virtio-9p share and guest access; demonstrated consequences include host code execution as the QEMU process user or a QEMU crash.
The record
- CVE
- CVE-2026-93834
- Published
- Sep 25, 2026
- Updated
- Sep 25, 2026
- Vendor
- Commonhaus Foundation
- Product
- Red Hat Enterprise Linux 10
- Classifications
- T1611
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 25, 2026CVE publishedPublication date reported by the CVE source.
- Sep 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
- QEMU 9pfs guest-escape reproducerfunctional · demonstrated
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Technologies
Your stack
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Your stack
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