Qemu-kvm: 9pfs: use-after-free race in tlcreate/twalk allows vm guest escape
Red Hat · Red Hat Enterprise Linux 10
8.8HighCVSS 3.1
Recommended action
Within 7 days
High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.
Published severityHigh→Operational priority:High, unchanged from published severity.unchanged
Evidence used
No CISA KEV confirmation is currently recorded.
A structured source references public exploit or proof-of-concept material.
Exploitation requires an existing local or physical foothold with privileges.
EPSS is 0.38% for the current model date.
Compensating controls
Restrict local access and enforce least privilege on affected hosts.
Increase monitoring for the attack path and post-exploitation behaviour described in the report.
Verification
Confirm that the asset runs Red Hat Red Hat Enterprise Linux 10 and falls inside the recorded affected range.
Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
Validate exposure, authentication requirements and compensating controls in the actual environment.
Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Distribution package intelligence
Release-specific package status
Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
5 package states
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
Distribution release
Source package
Vendor state
Fixed version
Evidence
Debian trixietrixie · source
qemu
Affected, no fix publishedDebian currently tracks this release as open.
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
The vendor explicitly identifies these products as affected by this CVE.
qemu as component of SUSE Linux Enterprise Desktop 15 SP7
qemu-img as component of SUSE Linux Enterprise Desktop 15 SP7
qemu-pr-helper as component of SUSE Linux Enterprise Desktop 15 SP7
qemu-tools as component of SUSE Linux Enterprise Desktop 15 SP7
qemu-vmsr-helper as component of SUSE Linux Enterprise Desktop 15 SP7
xen as component of SUSE Linux Enterprise Desktop 15 SP7
xen-libs as component of SUSE Linux Enterprise Desktop 15 SP7
xen-tools-domU as component of SUSE Linux Enterprise Desktop 15 SP7
qemu as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-arm as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-audio-alsa as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-audio-oss as component of SUSE Linux Enterprise High Performance Computing 12 SP5
Summary
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
No remediation text is recorded.
CVE-2026-93834 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityqemu-kvm: 9pfs: use-after-free race in Tlcreate/Twalk allows VM guest escape
80 known affected
The vendor explicitly identifies these products as affected by this CVE.
qemu-guest-agent as a component of Red Hat Enterprise Linux 10
qemu-img as a component of Red Hat Enterprise Linux 10
qemu-kvm as a component of Red Hat Enterprise Linux 10
qemu-kvm-audio-pa as a component of Red Hat Enterprise Linux 10
qemu-kvm-block-blkio as a component of Red Hat Enterprise Linux 10
qemu-kvm-block-curl as a component of Red Hat Enterprise Linux 10
qemu-kvm-block-rbd as a component of Red Hat Enterprise Linux 10
qemu-kvm-common as a component of Red Hat Enterprise Linux 10
qemu-kvm-core as a component of Red Hat Enterprise Linux 10
qemu-kvm-device-display-virtio-gpu as a component of Red Hat Enterprise Linux 10
qemu-kvm-device-display-virtio-gpu-ccw as a component of Red Hat Enterprise Linux 10
qemu-kvm-device-display-virtio-gpu-pci as a component of Red Hat Enterprise Linux 10
Summary
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
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.
Optional official sources
National CERT insights ?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.
Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.
Official European source
ENISA European Vulnerability Database
Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.
1 current
ENISA EUVD identifier
EUVD-2026-87092
No EUVD known-exploited evidence
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.
EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
8.8 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days
High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.
Fix not verified
01
What, why and how
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.
What
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.
Why
The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.
How
An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
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.
Why
The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.
How
An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation ?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No confirmed evidence
No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material ?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.Reference recorded
CISA Vulnrichment records proof-of-concept exploitation in its SSVC data. BlackTree has not independently executed or validated exploit material.
Likely attack path
local access → Use After Free → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Local
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Changed: exploitation can affect a different security authority
Weakness ?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-416: Use After Free. The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
CVSS vector ?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SChangedScope: The attack can affect a component governed by a different security authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
CWE-416Public exploit reference
A
Official authority intelligence
Only matched European and national findings are included. Language selectors and unavailable sources are omitted.
ENISA EUVD · EUVD-2026-87092Official EUVD mapping
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.
Official EUVD record ↗BSI · German · WID-SEC-2026-3598QEMU: Schwachstelle ermöglicht Ausführen von beliebigem Programmcode mit Benutzerrechten
Ein lokaler Angreifer kann eine Schwachstelle in QEMU ausnutzen, um beliebigen Programmcode mit Benutzerrechten auszuführen, Sicherheitsmaßnahmen zu umgehen und Daten zu manipulieren oder offenzulegen.
Operational remediation based on structured source evidence.
Status ?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix not verified
Affected
qemu as component of SUSE Linux Enterprise Desktop 15 SP7
qemu-img as component of SUSE Linux Enterprise Desktop 15 SP7
qemu-pr-helper as component of SUSE Linux Enterprise Desktop 15 SP7
qemu-tools as component of SUSE Linux Enterprise Desktop 15 SP7
qemu-vmsr-helper as component of SUSE Linux Enterprise Desktop 15 SP7
xen as component of SUSE Linux Enterprise Desktop 15 SP7
xen-libs as component of SUSE Linux Enterprise Desktop 15 SP7
xen-tools-domU as component of SUSE Linux Enterprise Desktop 15 SP7
qemu as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-arm as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-audio-alsa as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-audio-oss as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-audio-pa as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-audio-sdl as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-block-curl as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-block-iscsi as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-block-rbd as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-block-ssh as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-guest-agent as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-ipxe as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-kvm as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-lang as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-ppc as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-s390 as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-seabios as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-sgabios as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-tools as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-ui-curses as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-ui-gtk as component of SUSE Linux Enterprise High Performance Computing 12 SP5
qemu-ui-sdl as component of SUSE Linux Enterprise High Performance Computing 12 SP5
and 1608 more
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04
Evidence and provenance
Published 25 Sept 2026 · Last source change 25 Sept 2026, 13:50 UTC · CWE-416 · Use After Free
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source ?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.FIRST · tracked since 2026-09-26
European sourceENISA EUVD · EUVD-2026-87092
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD awaiting enrichment
Core structured fields are present and their contributing authorities are shown above.
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.