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Response snapshot Oct 26, 2026, 22:09 UTC

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VulnerabilityCVE-2026-113711

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

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:

Published Updated

At a glance

Exploited
Not known
Severity
7.5 High (CVSS 3.1)
Chance of exploitation
0.6% in the next 30 days
Sources
2 independent sources

What to do

GitHub lists first patched versions: apostrophe: 4.33.0; @apostrophecms/import-export: 3.7.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-86wm-68pq-5jwq (opens a new tab)

What happened

## 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()`

Continue reading

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/ - - `

### 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 /tmp/chunk.bin

curl -s -X POST \ 'http://localhost:3000/api/v1/@apostrophecms/page/importExportImport?aposBigUpload[type]=chunk&aposBigUpload[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]= ' ```

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/

Affected package ranges reported by GitHub: apostrophe: < 4.33.0 @apostrophecms/import-export: < 3.7.0

Scores and how they were measured

CVSS base severity

7.5

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.6%

Scored Percentile 46.4%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-86wm-68pq-5jwq (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-86wm-68pq-5jwq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    NVD CVE-2026-113711 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  13. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  14. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-113711, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 21). ApostropheCMS: Unauthenticated resource exhaustion via pre-auth aposBigUpload processing in @apostrophecms/import-export (CVE-2026-113711). https://kevwire.com/record/CVE-2026-113711

MLA

"ApostropheCMS: Unauthenticated resource exhaustion via pre-auth aposBigUpload processing in @apostrophecms/import-export (CVE-2026-113711)." KEVWire, 21 Oct. 2026, kevwire.com/record/CVE-2026-113711.

Chicago

KEVWire. "ApostropheCMS: Unauthenticated resource exhaustion via pre-auth aposBigUpload processing in @apostrophecms/import-export (CVE-2026-113711)." Last modified October 21, 2026. https://kevwire.com/record/CVE-2026-113711.

Evidence summary (plain text)

ApostropheCMS: Unauthenticated resource exhaustion via pre-auth aposBigUpload processing in @apostrophecms/import-export (Oct 21, 2026).
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:
CVSS 7.5 (version 3.1; evidence as of Oct 21, 2026; https://github.com/advisories/GHSA-86wm-68pq-5jwq).
EPSS 0.6% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-113711&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-86wm-68pq-5jwq: https://github.com/advisories/GHSA-86wm-68pq-5jwq
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNTo1Mjo1NlrOAAfxiA%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNDowNjoxNFrOAAfxZw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQwODoyNzoyM1rOAAYp9A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozNTo1OFrOAAfwCQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozMDoxM1rOAAfv2A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyODowOVrOAAfv1g%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyNDoyMFrOAAfv1Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDo0NTowN1rOAAfvzQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDozMDoyNlrOAAfvxw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDowMzo1N1rOAAfvxQ%3D%3D
NVD CVE-2026-113711: https://nvd.nist.gov/vuln/detail/CVE-2026-113711
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=6000
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-113711&date=2026-10-26
Record ID: CVE-2026-113711.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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