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

Moderate severity GitHub Reviewed Published Apr 23, 2026 in chainguard-dev/melange • Updated Apr 23, 2026

Package

gomod chainguard.dev/melange (Go)

Affected versions

>= 0.32.0, < 0.43.4

Patched versions

0.43.4

Description

Impact

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.

Patches

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).

Workarounds

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.

Credits

melange thanks Oleh Konko (@1seal from 1seal.org) for discovering and reporting this issue.

References

@antitree antitree published to chainguard-dev/melange Apr 23, 2026
Published to the GitHub Advisory Database Apr 23, 2026
Reviewed Apr 23, 2026
Last updated Apr 23, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(4th percentile)

Weaknesses

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

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. Learn more on MITRE.

CVE ID

CVE-2026-29051

GHSA ID

GHSA-q2pw-xx38-p64j

Source code

Credits

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