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

CVE-2026-42574

Low
0/10

Summary

In apko versions from 0.14.8 prior to 1.2.5, 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.

  • LOW
  • NETWORK
  • HIGH
  • UNCHANGED
  • NONE
  • NONE
  • NONE
  • NONE

CWE-22 - Path Traversal

Path traversal (or directory traversal), is a vulnerability that allows malicious users to traverse the server's root directory, gaining access to arbitrary files and folders such as application code & data, back-end credentials, and sensitive operating system files. In the worst-case scenario, an attacker could potentially execute arbitrary files on the server, resulting in a denial of service attack. Such an exploit may severely impact the integrity, confidentiality, and availability of an application.

References

Advisory Timeline

  • Published