apko dirFS has a symlink-following path traversal that allows multiple entry points to escape the build root

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-42574: 0.35% estimated exploitation activity in the next 30 days; percentile 28.93 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact A crafted .apk could install a TypeSymlink tar entry whose target pointed outside the build root, and a subsequent directory-creation or file-write entry in the same or later archive could traverse that symlink to reach host paths the build user could write to. The root cause was the sanitizePath helper in pkg/apk/fs/rwosfs.go, which rejected only lexical .. traversal and did not resolve or refuse symlinks. Every disk-backed DirFS method that handed its caller-supplied path to a symlink-following stdlib call — ReadFile, WriteFile, Chmod, Chown, Chtimes, MkdirAll, Mkdir, and Mknod — was affected. The reachable primitive from a malicious APK during tar extraction is the MkdirAll / Mkdir / WriteFile chain via apko build-cpio and disk-backed consumers such as melange; the remaining sinks are reachable by direct callers of the pkg/apk/fs package. The in-memory tarfs install path used by apko build, apko publish, and apko build-minirootfs is not affected. Patches Fixed in apko…

Published by the source

4 May 2026, 21:26 UTC

Last modified by the source

13 May 2026, 13:42 UTC

Source last checked

26 Oct 2026, 15:20 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-qq3r-w4hj-gjp6

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# Patch Next advisory brief: CVE-2026-42574

Advisory: apko dirFS has a symlink-following path traversal that allows multiple entry points to escape the build root
IDs: CVE-2026-42574, GHSA-qq3r-w4hj-gjp6
Record: https://patchnext.com/advisories/cve-2026-42574 (revision 1, source checked 26 Oct 2026, 15:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: chainguard.dev/apko 1.2.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go chainguard.dev/apko: affected >= 0.14.8, < 1.2.5; fixed in 1.2.5

## Suggested inspection (read-only)
- Go chainguard.dev/apko: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on chainguard.dev/apko.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-qq3r-w4hj-gjp6 (GitHub-reviewed advisory GHSA-qq3r-w4hj-gjp6 lists affected ranges: Go chainguard.dev/apko >=0.14.8 <1.2.5)

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