chainguard-dev melange up to 0.43.3 filepath.Separator pkgname path traversal

Summaryinfo

A vulnerability classified as critical was found in chainguard-dev melange up to 0.43.3. This affects the function filepath.Separator. Such manipulation of the argument pkgname leads to path traversal. This vulnerability is referenced as CVE-2026-29051. The attack can only be performed from a local environment. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in chainguard-dev melange up to 0.43.3 and classified as critical. Affected by this issue is the function filepath.Separator. The manipulation of the argument pkgname with an unknown input leads to a path traversal vulnerability. Using CWE to declare the problem leads to CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Impacted is integrity, and availability. CVE summarizes:

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---r.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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-29051 since 03/03/2026. The exploitation is known to be easy. The attack needs to be approached locally. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1006.

Upgrading to version 0.43.4 eliminates this vulnerability. Applying the patch 84f3b450ce6e472c4abb8dc4c26d0ce8ac1259ac is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• chainguard-dev

Name

• melange

Version

• 0.43.0
• 0.43.1
• 0.43.2
• 0.43.3

License

• open-source

Website

• Product: https://github.com/chainguard-dev/melange/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion