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BuildkitApplication · Mobyproject

CVE-2026-33747

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-27
Fix available
A fix is available. Upgrade to 0.28.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

This is a path traversal vulnerability in BuildKit versions prior to 0.28.1 where a malicious custom frontend image can craft API messages to write files outside the BuildKit state directory into arbitrary locations on the host system. The attack vector requires the use of `#syntax` directive or `--build-arg BUILDKIT_SYNTAX` with an untrusted custom frontend image.

MitigationUpgrade BuildKit to version 0.28.1 or later, and ensure only trusted frontend images (such as the official docker/dockerfile) are used rather than untrusted custom frontends.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
BuildkitApplication
Affected:< 0.28.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify BuildKit version
    Run `buildctl --version` or check the BuildKit container/image version. If using Docker, check the dockerd daemon version or BuildKit version via `docker buildx version` and `docker buildx inspect`.
    Affected if The installed BuildKit version is earlier than 0.28.1
  2. Audit Dockerfiles for custom frontend syntax directive
    Search all Dockerfile* files for the pattern `#syntax=` at the top of the file using `grep -r "^#syntax=" .` or similar file search commands.
    Affected if Any Dockerfile contains a `#syntax` directive pointing to a custom/untrusted frontend image
  3. Audit build arguments for custom frontend
    Search build logs, CI/CD configurations, or build scripts for usage of `--build-arg BUILDKIT_SYNTAX=` or `BUILDKIT_SYNTAX` environment variable set to a custom image reference.
    Affected if Builds invoke BuildKit with BUILDKIT_SYNTAX set to an unofficial/custom image
  4. Identify trusted vs untrusted frontend images
    For any custom frontend detected in steps 2 or 3, verify the image source. Inspect the image reference (e.g., `myregistry/myfrontend:latest`) and confirm it is the official docker/dockerfile image from Docker Hub or a trusted source.
    Affected if The custom frontend image is not from the official docker/dockerfile repository or is from an untrusted source

You are affected if BuildKit version is below 0.28.1 AND any build uses a custom/untrusted frontend image via #syntax directive or BUILDKIT_SYNTAX build argument.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.28.1 or later
Fixed in 0.28.1
Interim mitigation

Upgrade BuildKit to version 0.28.1 or later, and ensure only trusted frontend images (such as the official docker/dockerfile) are used rather than untrusted custom frontends.

Recommended fix High confidence

BuildKit v0.28.1

  1. Identify all BuildKit instances in your environment and their current version numbers
  2. For Docker/Moby users: Check the BuildKit version being used (e.g., docker version output shows BuildKit version)
  3. For standalone BuildKit users: Run `buildkitd --version` to check the current version
  4. If the version is below 0.28.1, upgrade BuildKit to version 0.28.1 or later
  5. If using Docker, ensure Docker Engine is updated to a version that bundles BuildKit 0.28.1 or later
  6. After upgrade, verify the new version by running the version check command again
  7. If using custom frontends via `#syntax` or `--build-arg BUILDKIT_SYNTAX`, ensure the frontend image is from a trusted source

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Buildkit Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-33747 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data