ApostropheCMS: Unauthenticated resource exhaustion via pre-auth aposBigUpload processing in @apostrophecms/import-export

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

ApostropheCMS is an open-source Node.js content management system. Prior to 4.33.0 of ApostropheCMS and 3.7.0 of the import-export module, import routes invoke bigUploadMiddleware without an early authorize callback, allowing unauthenticated requests to perform upload initialization, chunk storage, temporary processing, and attacker-declared cleanup work before the later user check rejects the import. This issue is fixed in ApostropheCMS 4.33.0 and import-export 3.7.0.

Source published

20 Oct 2026 17:49:31 UTC

Source modified

20 Oct 2026 19:04:07 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

ApostropheCMS is an open-source Node.js content management system. Prior to 4.33.0 of ApostropheCMS and 3.7.0 of the import-export module, import routes invoke bigUploadMiddleware without an early authorize callback, allowing unauthenticated requests to perform upload initialization, chunk storage, temporary processing, and attacker-declared cleanup work before the later user check rejects the import. This issue is fixed in ApostropheCMS 4.33.0 and import-export 3.7.0.

Source published

Oct 20, 2026, 5:49:31 PM (timezone not stated)

Source modified

Oct 20, 2026, 7:04:07 PM (timezone not stated)

Observed here

7 Nov 2026 04:34:48 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

ApostropheCMS is an open-source Node.js content management system. Prior to 4.33.0 of ApostropheCMS and 3.7.0 of the import-export module, import routes invoke bigUploadMiddleware without an early authorize callback, allowing unauthenticated requests to perform upload initialization, chunk storage, temporary processing, and attacker-declared cleanup work before the later user check rejects the import. This issue is fixed in ApostropheCMS 4.33.0 and import-export 3.7.0.

Source published

20 Oct 2026 18:17:21 UTC

Source modified

20 Oct 2026 19:53:10 UTC

Observed here

25 Oct 2026 05:17:18 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

## Summary A potential unauthenticated denial-of-service vulnerability exists in the chunked import upload path used by `@apostrophecms/import-export`. The affected import API routes invoke: `self.apos.http.bigUploadMiddleware()` before the actual import handler performs its authentication check. Because no `authorize` callback is supplied to `bigUploadMiddleware()`, unauthenticated requests can reach the `aposBigUpload` `start`, `chunk`, and `end` operations before the later `req.user` check rejects the import. As a result, an unauthenticated remote attacker can create server-side upload state, write chunk data to upload storage, trigger temporary-file processing, and cause attacker-controlled cleanup operations before authentication is enforced. ## Affected Component Package: `@apostrophecms/import-export` Confirmed affected version: `3.6.2` Potential earlier affected versions: The issue may affect earlier 3.x releases in which the current big-upload-based import implementation is present. I have not yet fully verified the exact introduction version and recommend that the maintainers confirm the affected version range. ## Vulnerability Type Primary: **CWE-400 — Uncontrolled Resource Consumption** Related: **CWE-306 — Missing Authentication for Critical Function** **CWE-770 — Allocation of Resources Without Limits or Throttling** ## Technical Details The page import route registers the following middleware chain: `packages/import-export/modules/@apostrophecms/import-export-page/index.js` ```javascript importExportImport: [ self.apos.http.bigUploadMiddleware(), async (req) => { return self.apos.modules['@apostrophecms/import-export'] .import(req, self.__meta.name); } ] ``` No `authorize` callback is passed to `bigUploadMiddleware()`. The `bigUploadMiddleware()` implementation explicitly supports an `authorize` callback and performs that authorization before processing the `aposBigUpload` protocol when supplied. Without that callback, requests containing: `aposBigUpload[type]=start` `aposBigUpload[type]=chunk` or `aposBigUpload[type]=end` are processed immediately. The actual authentication check occurs later in: `packages/import-export/lib/methods/import.js` ```javascript async import(req, moduleName) { if (!req.user) { throw self.apos.error('forbidden'); } ``` This means authentication occurs only after the chunked-upload middleware has already performed server-side work. ## Attack Flow ### 1. Start An unauthenticated attacker submits an `aposBigUpload[type]=start` request. The server generates an upload ID and stores attacker-supplied upload metadata, including the declared `chunks` count. ### 2. Chunk The attacker can upload chunk data. `bigUploadChunk()` copies attacker-controlled data into: `/big-uploads/<id>-<n>-<chunk>` ### 3. End The attacker sends an `aposBigUpload[type]=end` request. `bigUploadEnd()` begins processing the upload and creates temporary files before invoking the downstream import handler. Only after this processing completes does execution reach the later authentication check in `import()`. ### 4. Cleanup amplification The attacker-controlled `chunks` value is also used by `bigUploadCleanupOne()`: ```javascript for (const { chunks } of Object.values(bigUpload.files)) { for (let i = 0; (i < chunks); i++) { await ufs.remove(...); } } ``` No small upper bound on the declared chunk count appears to be enforced at upload initialization. This allows an unauthenticated attacker to increase the number of filesystem cleanup operations performed for an upload. ## Proof of Concept The following reproduction was performed only against an isolated test environment. ### Start an upload without authentication ```bash curl -s -X POST \ 'http://localhost:3000/api/v1/@apostrophecms/page/importExportImport?aposBigUpload[type]=start' \ -H 'Content-Type: application/json' \ --data '{"files":{"file":{"name":"evil.tar.gz","size":4,"type":"application/gzip","chunks":1}}}' ``` The server returns an upload ID despite the request having no authenticated session. ### Upload a chunk ```bash printf 'PWN!' >/tmp/chunk.bin curl -s -X POST \ 'http://localhost:3000/api/v1/@apostrophecms/page/importExportImport?aposBigUpload[type]=chunk&aposBigUpload[id]=<ID>&aposBigUpload[n]=0&aposBigUpload[chunk]=0' \ -F 'chunk=@/tmp/chunk.bin;type=application/octet-stream' ``` The request succeeds and causes server-side upload storage to be used. ### Finalize the upload ```bash curl -i -X POST \ 'http://localhost:3000/api/v1/@apostrophecms/page/importExportImport?aposBigUpload[type]=end&aposBigUpload[id]=<ID>' ``` Observed behavior: * `start` returns HTTP 200 and an upload ID without authentication. * `chunk` returns HTTP 200 and results in server-side chunk storage. * `end` eventually reaches the downstream authentication check and is rejected. * However, the server-side big-upload processing has already occurred before that authentication rejection. In my isolated harness: * `chunks=1` resulted in one cleanup removal attempt. * `chunks=50` resulted in 50 cleanup removal attempts. This demonstrates that the attacker-controlled chunk count directly influences server-side cleanup work. ## Security Impact The vulnerability allows an unauthenticated remote attacker to cause server-side storage and filesystem operations that should only be reachable by authorized import users. Possible consequences include: * Consumption of upload and temporary storage. * Creation of server-side upload state by unauthenticated users. * Repeated filesystem I/O. * Cleanup amplification based on attacker-controlled chunk counts. * Potential service degradation or denial of service when the attack is repeated or sufficiently amplified. ## Root Cause Authentication is enforced in the downstream import handler rather than before the chunked-upload middleware. The middleware itself already supports an `authorize` callback specifically for preventing unauthorized use of the big-upload functionality. ## Suggested Remediation Require authentication before any `aposBigUpload` operation is processed. For example: * Pass an appropriate `authorize` callback to `bigUploadMiddleware()` on all import routes. * Reject unauthenticated users before `start`, `chunk`, or `end`. * Enforce reasonable limits on declared chunk counts. * Validate declared size against actual uploaded data. * Introduce per-user and global storage/rate limits. * Ensure temporary files are removed when downstream processing fails. * Add regression tests confirming that anonymous `start`, `chunk`, and `end` requests are rejected before upload state or files are created. Relevant reviewed commit: `d3ff8c9bb001be1acf7fdc3f035190250ac64b45` ## Researcher Credit **Kai Zhi** GitHub: **https://github.com/kaizhi888**

Source published

21 Oct 2026 13:51:21 UTC

Source modified

21 Oct 2026 14:00:27 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH