melange has Path Traversal via .PKGINFO in --persist-lint-results

Summary

melange allows users to build apk packages using declarative pipelines. Starting in version 0.32.0 and prior to version 0.43.4, `melange lint --persist-lint-results` (opt-in flag, also usable via `melange build --persist-lint-results`) constructs output file paths by joining `--out-dir` with the `arch` and `pkgname` values read from the `.PKGINFO` control file of the APK being linted. In affected versions these values were not validated for path separators or `..` sequences, so an attacker who can supply an APK to a melange-based lint/build pipeline (e.g. CI that lints third-party APKs, or build-as-a-service) could cause melange to write `lint-<pkgname>-<pkgver>-r<epoch>.json` to an arbitrary `.json` path reachable by the melange process. The written file is a JSON lint report whose content is partially attacker-influenced. There is no direct code-execution path, but the write can clobber other JSON artifacts on the filesystem. The issue only affects deployments that explicitly pass `--persist-lint-results`; the flag is off by default. The issue is fixed in melange v0.43.4 by validating `arch` and `pkgname` for `..`, `/`, and `filepath.Separator` before path construction in `pkg/linter/results.go` (commit 84f3b45). As a workaround, do not pass `--persist-lint-results` when linting or building APKs whose `.PKGINFO` contents are not fully trusted. Running melange as a low-privileged user and confining writes to an isolated directory also limits impact.

Timeline

1. Apr 24, 2026, 12:00 AM UTCCVE published
2. Apr 24, 2026, 1:10 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Apr 24, 2026, 1:10 PM UTCRecord last updated

Affected versions

• chainguard-dev melange

  From 0.32.0 · fixed in 0.43.4

• chainguard.dev/melangeGo

  From 0.32.0 · fixed in 0.43.4

References 2