CVE-2026-29050

Description

melange allows users to build apk packages using declarative pipelines. Starting in version 0.32.0 and prior to version 0.43.4, 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. The issue is 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. As a workaround, 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 `/`.

CVSS Details

CVSS Score

6.1

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N

Configurations (Affected Products)

cpe:2.3:a:chainguard:melange:*:*:*:*:*:go:*:* - VULNERABLE

melange 0.32.0 至 0.43.4 之前

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

# Malicious melange configuration file
package:
  name: exploit
  version: 1.0
pipeline:
  - uses: ../../../etc/passwd  # Path traversal attempt
    runs: |
      cat /etc/passwd
# Note: This PoC is for demonstration purposes only. Actual exploitation requires adjustment based on the specific environment and melange configuration.

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-29050
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-29050
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-29050/
[4] VulDB https://vuldb.com/cve/CVE-2026-29050
[5] https://github.com/chainguard-dev/melange/security/advisories/GHSA-98f2-w9h9-7fp9

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-29050", "sourceIdentifier": "[email protected]", "published": "2026-04-24T00:16:27.303", "lastModified": "2026-04-27T14:31:58.970", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "melange allows users to build apk packages using declarative pipelines. Starting in version 0.32.0 and prior to version 0.43.4, 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. The issue is 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. As a workaround, 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 `/`."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N", "baseScore": 6.1, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.8, "impactScore": 4.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-22"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:chainguard:melange:*:*:*:*:*:go:*:*", "versionStartIncluding": "0.32.0", "versionEndExcluding": "0.43.4", "matchCriteriaId": "3E8363CF-5AF6-4FD7-A491-5D3E8E1F3576"}]}]}], "references": [{"url": "https://github.com/chainguard-dev/melange/security/advisories/GHSA-98f2-w9h9-7fp9", "source": "[email protected]", "tags": ["Mitigation", "Patch", "Vendor Advisory"]}]}}