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Path traversal in apko dirFS allows filesystem writes outside base

High
antitree published GHSA-5g94-c2wx-8pxw Feb 3, 2026

Package

gomod chainguard.dev/apko (Go)

Affected versions

>= v0.14.8, < v1.1.1

Patched versions

v1.1.1

Description

A path traversal vulnerability was discovered in apko's dirFS filesystem abstraction. An attacker who can supply a malicious APK package (e.g., via a compromised or typosquatted repository) could create directories or symlinks outside the intended installation root. The MkdirAll, Mkdir, and Symlink methods in pkg/apk/fs/rwosfs.go use filepath.Join() without validating that the resulting path stays within the base directory.

Fix: Fixed by d8b7887. Merged into release.

Acknowledgements

Thank you to Oleh Konko from 1seal for discovering and reporting this issue.

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

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

CVE ID

CVE-2026-25121

Weaknesses

Relative Path Traversal

The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as .. that can resolve to a location that is outside of that directory. Learn more on MITRE.

Credits