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Fencer Intel
medium 4.5

CVE-2026-121520 json

Malicious client could set xattr value outside of BuildKit state directory

published 6d ago modified 3d ago also EUVD-2026-116538

cvss
4.5
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

In BuildKit versions prior to v0.34.1, a malicious client with access to the BuildKit control APIs can submit a build request that sets an extended attribute on a file outside the BuildKit state directory. Extended attributes in the trusted. or security. namespaces may also be set, potentially giving a program on the host elevated privileges. This issue affects build services that accept build requests from untrusted users. The issue is fixed in v0.34.1.

Patch / fix

  • Moby BuildKit 0.34.1

Is CVE-2026-121520 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-121520 updated cvss 7.9

github.com/moby/buildkit: BuildKit: Privilege escalation via unauthorized extended file attribute modification

  • Red Hat DPU kit for NVIDIA dpu-kit-for-nvidia/must-gather-rhel10, dpu-kit-for-nvidia/bluefield-ocp-layer-rhel10 Red Hat NVIDIA JetPack 7 for RHEL nvidia/nvidia-jetpack-for-rhel10 Red Hat OpenShift Developer Tools and Services ocp-tools-4/jenkins-rhel8, ocp-tools-4/jenkins-rhel9, ocp-tools-4/jenkins-agent-base-rhel8, ocp-tools-4/jenkins-agent-base-rhel9 Red Hat OpenShift Source-to-Image (S2I) source-to-image/source-to-image-rhel8, source-to-image/source-to-image-rhel9 Red Hat Pen Drive Powered by Red Hat Lightspeed pen-drive/pen-drive-scanner-rhel9
    affected: workaround, no fix available
  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-24/ee-supported-rhel8, ansible-automation-platform-24/ee-supported-rhel9, ansible-automation-platform-25/ee-supported-rhel8, ansible-automation-platform-25/ee-supported-rhel9, ansible-automation-platform-26/ee-supported-rhel9, ansible-automation-platform-27/ee-supported-rhel9, +10 more
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Build of Podman Desktop rh-podman-desktop 3c6fc75a2a6cf5bb9b8a667fddcbbf428132badc
    affected: workaround, no fix available
  • Red Hat Ceph Storage 9 rhceph/alloy-rhel10
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Certification Program for Red Hat Enterprise Linux 9 rhcertification/redhat-certification-baremetal, rhcertification/redhat-certification-system-ai-10 Red Hat Developer Hub 1 rhdh/rhdh-must-gather-rhel9 Red Hat Enterprise Linux 8 podman, buildah, podman-tests, buildah-tests, podman-docker, podman-remote, +4 more Red Hat Enterprise Linux 9 podman, buildah, podman-tests, buildah-tests, podman-docker, podman-remote, +5 more Red Hat Enterprise Linux 10 ubi10/podman, ubi10/buildah, podman 6.1.0-2.el10, buildah 1.45.0-2.el10 Red Hat OpenShift AI (RHOAI) rhoai/rhai-cli-rhel9, rhoai/odh-must-gather-rhel9, rhoai/odh-ai-gateway-payload-processing-e2e-rhel9
    +6 more products
    Red Hat Openshift Data Foundation 4 odf4/mcg-core-rhel9, odf4/odf-must-gather-rhel9 Red Hat OpenShift Dev Spaces devspaces/udi-rhel9, devspaces/udi-base-rhel9, devspaces/udi-base-rhel10 Red Hat OpenShift GitOps openshift-gitops-1/must-gather-rhel9 Red Hat OpenStack Platform 18.0 rhoso-operators/openstack-must-gather-rhel9, rhoso-operators/prometheus-podman-exporter-rhel9 Red Hat Trusted Artifact Signer rhtas/ec-rhel9 Red Hat Web Terminal web-terminal/web-terminal-tooling-rhel9
    affected: workaround, no fix available
  • Red Hat Hardened Images podman 6.1.4-1.3.hum1, podmansh 6.1.4-1.3.hum1, podman-docker 6.1.4-1.3.hum1, podman-remote 6.1.4-1.3.hum1, podman-machine 6.1.4-1.3.hum1
    fixed: vendor fix RHSA-2026:95611
  • Red Hat Assisted Installer for Red Hat OpenShift Container Platform 2 rhai/assisted-installer-controller-rhel9, assisted/agent-preinstall-image-builder-rhel9 Red Hat Compliance Operator compliance/openshift-compliance-must-gather-rhel8 Red Hat Confidential Compute Attestation build-of-trustee/trustee-must-gather-rhel9, openshift-sandboxed-containers/osc-must-gather-rhel9, openshift-sandboxed-containers/osc-podvm-builder-rhel9 Red Hat Custom Metric Autoscaler operator for Red Hat Openshift custom-metrics-autoscaler/custom-metrics-autoscaler-rhel9-operator Red Hat Kernel Module Management Operator for Red Hat Openshift kmm/kernel-module-management-must-gather-rhel9 Red Hat Logical Volume Manager Storage lvms4/lvms-must-gather-rhel8, lvms4/lvms-must-gather-rhel9
    +12 more products
    Red Hat Migration Toolkit for Applications 8 mta/mta-cli-rhel9, mta/mta-discovery-addon-rhel9 Red Hat Migration Toolkit for Containers rhmtc/openshift-migration-log-reader-rhel8, rhmtc/openshift-migration-must-gather-rhel8 Red Hat Migration Toolkit for Virtualization migration-toolkit-virtualization/mtv-must-gather-rhel8, migration-toolkit-virtualization/mtv-must-gather-rhel9 Red Hat Multicluster Engine for Kubernetes multicluster-engine/must-gather-rhel9, multicluster-engine/assisted-service-8-rhel8, multicluster-engine/assisted-service-9-rhel9, multicluster-engine/assisted-installer-controller-rhel9 Red Hat Node HealthCheck Operator workload-availability/node-healthcheck-must-gather-rhel8, workload-availability/node-healthcheck-must-gather-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-agentic-sandbox-rhel9, openshift-lightspeed-tech-preview/lightspeed-rag-tool-rhel9 Red Hat OpenShift Serverless openshift-serverless-1/kn-client-kn-rhel9, openshift-serverless-clients 1.17.0-4.el9, openshift-serverless-1/serverless-must-gather-rhel9, openshift-serverless-1/kn-plugin-func-func-util-rhel9 Red Hat OpenShift Service Mesh 3 istio-proxy-selinux, istio-proxy 1.30.5-1.el9, openshift-service-mesh/istio-cni-rhel9, openshift-service-mesh/istio-pilot-rhel9, openshift-service-mesh/istio-proxyv2-rhel9, openshift-service-mesh/istio-must-gather-rhel9 Red Hat Advanced Cluster Management for Kubernetes 2 rhacm2/acm-must-gather-rhel9 Red Hat Build of Kueue kueue/kueue-must-gather-rhel9 Red Hat Edge Manager 1 rhem/flightctl-imagebuilder-worker-rhel10 Red Hat Hardened Images buildah 1.45.0-2.el10, trivy 0.76.1-0.2.hum1
    not affected: vulnerable code not present
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-th06-cpu-torch291-py312-rhel9, rhoai/odh-th06-cuda130-torch291-py312-rhel9
    not affected: component not present

5 more not affected in the full advisory

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3d ago

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 4.5 CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H
CNA 4.0 4.5 CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • Moby BuildKit

Classification

Weakness
  • CWE-61 UNIX Symbolic Link (Symlink) Following

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.