BuildKit's Malicious frontend can cause file escape outside of storage root (CVE-2026-33747) | HOL Guard CVE

High · CVSS 8.4CVE-2026-33747GHSA-4C29-8RGM-JVJJ

BuildKit's Malicious frontend can cause file escape outside of storage root

Answer in brief

CVE-2026-33747 records a High severity (CVSS 8.4) vulnerability in BuildKit's Malicious frontend can cause file escape outside of storage root. The current sources do not mark it as known exploited. The current feed maps github.com/moby/buildkit (go). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Mar 26, 2026Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Sep 10, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.4
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 8.4. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps github.com/moby/buildkit (go). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
github.com/moby/buildkitgo	>=0 <0.28.1	0.28.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for github.com/moby/buildkit.
Review the reported fix. Update github.com/moby/buildkit to 0.28.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Mar 26, 2026
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Sep 10, 2026

Sources and claim methodology

Upstream source description

### Impact 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. ### Patches The issue has been fixed in v0.28.1+ ### Workarounds Issue 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.

Quoted source text, attributed separately from HOL analysis.