CVE-2026-33747 BuildKit vulnerable to malicious frontend causing file escape outside of storage root
A malicious BuildKit frontend can write files outside the storage root, requiring the use of untrusted custom frontends.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33747?
CVE-2026-33747 is a high-severity path traversal vulnerability in moby buildkit, published on 27 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
BuildKit is a toolkit for converting source code to build artifacts in an efficient, expressive and repeatable manner. Prior to version 0.28.1, when using a custom BuildKit frontend, the frontend can craft an API message that causes files to be written outside of the BuildKit state directory for the execution context. The issue has been fixed in v0.28.1. The vulnerability requires using an untrusted BuildKit frontend set with `#syntax` or `--build-arg BUILDKIT_SYNTAX`. Using these options with a well-known frontend image like `docker/dockerfile` is not affected.
Weakness: CWE-22
Which versions are affected by CVE-2026-33747?
3 open source packages ship an affected version, including github.com/moby/buildkit. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/moby/buildkit Go | All versions | 0.28.1 |
github.com/moby/buildkit Go | All versions | 0.28.1 |
github.com/moby/buildkit Go | All versions | 0.28.1 |
Linux distribution packages (2)
conftest openSUSE:Tumbleweed | All versions | 0.67.1-2.1 |
tailscale openSUSE:Tumbleweed | All versions | 1.96.4-1.1 |
Products include Mobyproject Buildkit.
How do I fix CVE-2026-33747?
Upgrade github.com/moby/buildkit to 0.28.1 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-33747 being exploited?
There is no known exploitation of CVE-2026-33747 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-2026-33748 BuildKit Git URL subdir component can cause access to restricted files
- CVE-2026-15789 Malicious client can bypass destination directory validation on local sources upload
Sources
Also known as BELL-CVE-2026-33747, CLEANSTART-2026-DU09908, CLEANSTART-2026-IP63543, CLEANSTART-2026-QH82064, CLEANSTART-2026-TB67127, DEBIAN-CVE-2026-33747 and 33 more.