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CVE Record

CVE-2026-47243: Kata guest escape: runtime-rs guest-root to host-root escape via virtiofs

Kata Containers is an open source project focusing on a standard implementation of lightweight Virtual Machines (VMs) that perform like containers. Prior to 3.31.0, the runtime-rs standalone virtio-fs path is vulnerable to a guest-root to host-root escape. In this configuration, Kata runs the host virtiofsd as root with --sandbox none --seccomp none, so an attacker with root-equivalent access inside the guest can bypass the guest virtio-fs client entirely by taking over the virtio-fs PCI device and building a virtqueue in userspace to submit raw FUSE requests directly to the host virtiofsd. A crafted FUSE_SYMLINK request whose new symlink name is an absolute host path is honored outside the configured shared directory, allowing guest root to create root-owned symlinks in sensitive host locations such as /etc/cron.d. By pointing such a symlink at a guest-controlled crontab payload reachable through a live runtime process's mount namespace, the attacker causes the host cron daemon to execute that payload as host root, crossing the Kata isolation boundary. This issue is fixed in version 3.31.0.

CriticalCVSS 9.2Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A flaw in a specific Kata Containers storage-sharing configuration can let an attacker who already controls a guest as root escape the virtual machine boundary and gain root-level control of the host. Successful exploitation could compromise the host and other workloads using it.

Executive priority

Treat affected multi-tenant or untrusted-workload hosts as an immediate remediation priority. The vulnerability crosses a core isolation boundary and can provide host-root control, although exploitation requires prior root-equivalent access inside the guest.

Technical view

Before version 3.31.0, the runtime-rs standalone virtio-fs path runs host virtiofsd as root without sandboxing or seccomp. Guest root can submit raw FUSE requests through the virtio-fs PCI device. Improper handling of absolute symlink names permits writes outside the shared directory, enabling guest-to-host privilege escalation.

Likely exposure

Exposure is limited to Kata Containers versions before 3.31.0 using the runtime-rs standalone virtio-fs path. Environments not using this specific configuration are not established as affected by the supplied evidence. Exploitation requires root-equivalent guest access.

Exploitation context

The supplied sources describe a technically credible guest-root to host-root escape. They do not establish active exploitation, and the CVE is not identified as included in KEV.

Researcher notes

The key scope constraint is the runtime-rs standalone virtio-fs configuration. The weakness combines insufficient virtiofsd isolation with absolute-path handling in FUSE symlink requests. The supplied evidence names 3.31.0 as fixed but provides no evidence of exploitation in the wild.

Mitigation direction

  • Upgrade affected Kata Containers deployments to version 3.31.0 or later.
  • Identify and prioritize hosts using runtime-rs with the standalone virtio-fs path.
  • Until upgraded, avoid running untrusted workloads in the affected configuration.
  • Review the vendor advisory for any additional supported operational guidance.

Validation and detection

  • Inventory Kata Containers versions across hosts and orchestration environments.
  • Confirm whether runtime-rs standalone virtio-fs is enabled on each deployment.
  • Verify upgraded systems report Kata Containers version 3.31.0 or later.
  • Review affected hosts for unexpected root-owned symlinks or sensitive host-file changes.
  • Investigate whether any untrusted workload obtained root-equivalent guest access.
Prepared
Confidence
high
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-22: File access and web shell behavior lookup

File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · low confidence lookup

CWE-36: Exact CWE lookup

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cve · low confidence lookup

CVE-2026-47243 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.2 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
2ADP providers
2Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: noTechnical Impact: total

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.2CVSS 4.0CriticalCVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N——GitHub_M

Vulnerability scoring details

Base CVSS 4.0 score

9.2Critical
CVSS 4.0 vector shape for CVE-2026-47243Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
kata-containerskata-containers< 3.31.0Listed
Weakness

CWE details

CWE-22CWE-36

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.