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

High severity GitHub Reviewed Published Mar 25, 2026 in moby/buildkit • Updated Mar 27, 2026

Package

gomod github.com/moby/buildkit (Go)

Affected versions

< 0.28.1

Patched versions

0.28.1

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.

References

@tonistiigi tonistiigi published to moby/buildkit Mar 25, 2026
Published to the GitHub Advisory Database Mar 26, 2026
Reviewed Mar 26, 2026
Published by the National Vulnerability Database Mar 27, 2026
Last updated Mar 27, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(17th percentile)

Weaknesses

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Learn more on MITRE.

CVE ID

CVE-2026-33747

GHSA ID

GHSA-4c29-8rgm-jvjj

Source code

Credits

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