CVE-2026-25121 apko is vulnerable to path traversal in apko dirFS which allows filesystem writes outside base

What is CVE-2026-25121?

CVE-2026-25121 is a high-severity path traversal vulnerability in chainguard-dev apko, published on 4 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

apko allows users to build and publish OCI container images built from apk packages. From version 0.14.8 to before 1.1.1, 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. This issue has been patched in version 1.1.1.

Weakness: CWE-22, CWE-23

Which versions are affected by CVE-2026-25121?

3 open source packages ship an affected version, including chainguard.dev/apko. It affects 1 product.

Products include Chainguard Apko.

How do I fix CVE-2026-25121?

Upgrade chainguard.dev/apko to 1.1.0 or later.

Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.

Is CVE-2026-25121 being exploited?

There is no known exploitation of CVE-2026-25121 in the wild and no public exploit code.

Other vulnerabilities in chainguard-dev apko

• CVE-2026-25140 apko affected by potential unbounded resource consumption in expandapk.ExpandApk on attacker-controlled .apk streams High 7.5
• CVE-2026-25122 apko is vulnerable to unbounded resource consumption in expandapk.Split on attacker-controlled .apk streams Medium 5.5

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-5g94-c2wx-8pxw, GO-2026-4405, MINI-fm7j-w2v8-v2mj.