GHSA-98f2-w9h9-7fp9 melange has Path Traversal When Resolving External Pipelines via Unvalidated pipeline[].uses

• Go chainguard.dev/melange: >= 0.32.0, < 0.43.4 → fixed in 0.43.4

Impact An attacker who can influence a melange configuration file — for example through pull-request-driven CI or build-as-a-service scenarios — could set `pipeline[].uses` to a value containing `../` sequences or an absolute path. The `(*Compiled).compilePipeline` function in `pkg/build/compile.go` passed `uses` directly to `filepath.Join(pipelineDir, uses + ".yaml")` without validating the value, so the resolved path could escape each `--pipeline-dir` and read an arbitrary YAML-parseable file visible to the melange process. Because the loaded file is subsequently interpreted as a melange pipeline and its `runs:` block is executed via `/bin/sh -c` in the build sandbox, this additionally allowed shell commands sourced from an out-of-tree file to run during the build, bypassing the review boundary that normally covers the in-tree pipeline definition. Patches Fixed in melange v0.43.4 via commit 5829ca4. The fix rejects `uses` values that are absolute paths or contain `..`, and verifies (via `filepath.Rel` after `filepath.Clean`) that the resolved target remains within the pipeline directory. Workarounds Only run `melange build` against configuration files from trusted sources. In CI systems that build user-supplied melange configs, gate builds behind manual review of `pipeline[].uses` values and reject any containing `..` or leading `/`. Credits melange thanks Oleh Konko (@1seal from 1seal.org) for discovering and reporting this issue.