EUVD-2026-46074Severity by source
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/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
AV:L because daemon socket access is required; AC:H for WCOW-specific prerequisite; S:C because junction traversal escapes container cache boundary to host filesystem.
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Primary rating from Vendor (Docker).
CVSS VectorVendor: Docker
Lifecycle Timeline
3DescriptionCVE.org
BuildKit's cache mount source= selector on Windows Container on Windows (WCOW) workers does not detect NTFS directory junctions placed inside the cache root. A build authored by an untrusted user on a WCOW-configured BuildKit daemon can read arbitrary host files reachable to the BuildKit daemon process.
AnalysisAI
Arbitrary host file disclosure in BuildKit's WCOW (Windows Container on Windows) worker mode allows an untrusted build author to read any file reachable by the BuildKit daemon process. By placing NTFS directory junctions inside the cache mount root - a technique the source= selector fails to detect on Windows - a malicious Dockerfile can redirect cache access to traverse outside the container's expected filesystem boundary. This affects any multi-tenant or shared CI/CD environment running a WCOW-configured BuildKit daemon where untrusted users can submit builds; no active exploitation has been confirmed (not listed in CISA KEV) and no public exploit code has been identified at time of analysis.
Technical ContextAI
BuildKit (CPE: cpe:2.3:a:moby:buildkit:*:*:*:*:*:*:*:*) is Docker's container image build engine. Its RUN --mount=type=cache,source=<dir> Dockerfile instruction allows builds to reuse a named cache directory across builds, improving performance. On Windows, NTFS supports 'directory junctions' - a form of filesystem reparse point functionally analogous to symlinks but specifically for directories. CWE-59 (Improper Link Resolution Before File Access, also known as 'Link Following') describes the root cause: the cache mount resolver on WCOW workers does not identify or reject NTFS junctions placed inside the designated cache root. When the daemon follows such a junction during a build, it resolves the junction target on the host filesystem rather than remaining within the cache sandbox. This is the Windows analogue of classic TOCTOU symlink attacks seen on Linux, and is specific to WCOW workers - Linux-based BuildKit workers are unaffected as they use a different filesystem model.
RemediationAI
Consult the official security advisory at https://github.com/moby/buildkit/security/advisories/GHSA-388v-wmr2-g2v2 for the patched BuildKit version; no specific fix version was present in the input data and none can be cited here without independent confirmation. Until a patch is applied, the most effective compensating control is to restrict access to WCOW-configured BuildKit daemons to fully trusted users only - removing untrusted contributor access to build submission eliminates the attack path entirely. A second mitigation is to disable cache mount usage (avoid --mount=type=cache,source=... directives) in builds from untrusted sources on WCOW workers; this reduces build performance but closes the specific code path. Switching affected pipelines to Linux-based BuildKit workers, where the vulnerability does not exist, is an alternative architectural mitigation where feasible. Running the BuildKit daemon under a minimally privileged Windows service account reduces the blast radius of exploitation by limiting which host files are reachable even if the junction traversal succeeds.
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Same weakness CWE-59 – Improper Link Resolution Before File Access
View allSame technique Information Disclosure
View allVendor StatusVendor
SUSE
Severity: Moderate| Product | Status |
|---|---|
| SUSE Linux Enterprise Server 16.1 | Not-Affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | Not-Affected |
| SUSE Linux Micro 6.0 | Not-Affected |
| SUSE Linux Micro 6.1 | Not-Affected |
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External POC / Exploit Code
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