CVE-2026-15788 WCOW cache mount source selector resolves NTFS junctions outside of cache root
An attacker can read arbitrary host files via NTFS junctions in BuildKit cache mounts on Windows Container on Windows workers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-15788?
CVE-2026-15788 is a medium-severity path traversal vulnerability in moby BuildKit, published on 20 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-59
Which versions are affected by CVE-2026-15788?
It affects 1 product.
Products include Mobyproject Buildkit.
How do I fix CVE-2026-15788?
Apply the vendor's patch.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-15788 being exploited?
There is no known exploitation of CVE-2026-15788 in the wild and no public exploit code.
Other vulnerabilities in moby BuildKit
- CVE-2024-23652 BuildKit possible host system access from mount stub cleaner
- CVE-2024-23653 BuildKit interactive containers API does not validate entitlements check
- CVE-2024-23651 BuildKit possible race condition with accessing subpaths from cache mounts
- CVE-2026-33747 BuildKit vulnerable to malicious frontend causing file escape outside of storage root
- CVE-2026-33748 BuildKit Git URL subdir component can cause access to restricted files
Sources
Also known as GHSA-388v-wmr2-g2v2.