Source: node-qs
Version: 6.14.1+ds+~6.14.0-1
Severity: important
Tags: security upstream
X-Debbugs-Cc: [email protected], Debian Security Team <[email protected]>
Hi,
The following vulnerability was published for node-qs.
CVE-2026-2391[0]:
| ### Summary The `arrayLimit` option in qs does not enforce limits
| for comma-separated values when `comma: true` is enabled, allowing
| attackers to cause denial-of-service via memory exhaustion. This is
| a bypass of the array limit enforcement, similar to the bracket
| notation bypass addressed in GHSA-6rw7-vpxm-498p (CVE-2025-15284).
| ### Details When the `comma` option is set to `true` (not the
| default, but configurable in applications), qs allows parsing comma-
| separated strings as arrays (e.g., `?param=a,b,c` becomes `['a',
| 'b', 'c']`). However, the limit check for `arrayLimit` (default: 20)
| and the optional throwOnLimitExceeded occur after the comma-handling
| logic in `parseArrayValue`, enabling a bypass. This permits creation
| of arbitrarily large arrays from a single parameter, leading to
| excessive memory allocation. **Vulnerable code** (lib/parse.js:
| lines ~40-50): ```js if (val && typeof val === 'string' &&
| options.comma && val.indexOf(',') > -1) { return val.split(',');
| } if (options.throwOnLimitExceeded && currentArrayLength >=
| options.arrayLimit) { throw new RangeError('Array limit
| exceeded. Only ' + options.arrayLimit + ' element' +
| (options.arrayLimit === 1 ? '' : 's') + ' allowed in an array.'); }
| return val; ``` The `split(',')` returns the array immediately,
| skipping the subsequent limit check. Downstream merging via
| `utils.combine` does not prevent allocation, even if it marks
| overflows for sparse arrays.This discrepancy allows attackers to
| send a single parameter with millions of commas (e.g.,
| `?param=,,,,,,,,...`), allocating massive arrays in memory without
| triggering limits. It bypasses the intent of `arrayLimit`, which is
| enforced correctly for indexed (`a[0]=`) and bracket (`a[]=`)
| notations (the latter fixed in v6.14.1 per GHSA-6rw7-vpxm-498p).
| ### PoC **Test 1 - Basic bypass:** ``` npm install qs ``` ```js
| const qs = require('qs'); const payload = 'a=' + ','.repeat(25);
| // 26 elements after split (bypasses arrayLimit: 5) const options =
| { comma: true, arrayLimit: 5, throwOnLimitExceeded: true }; try {
| const result = qs.parse(payload, options);
| console.log(result.a.length); // Outputs: 26 (bypass successful) }
| catch (e) { console.log('Limit enforced:', e.message); // Not
| thrown } ``` **Configuration:** - `comma: true` - `arrayLimit: 5` -
| `throwOnLimitExceeded: true` Expected: Throws "Array limit
| exceeded" error. Actual: Parses successfully, creating an array of
| length 26. ### Impact Denial of Service (DoS) via memory
| exhaustion.
If you fix the vulnerability please also make sure to include the
CVE (Common Vulnerabilities & Exposures) id in your changelog entry.
For further information see:
[0] https://security-tracker.debian.org/tracker/CVE-2026-2391
https://www.cve.org/CVERecord?id=CVE-2026-2391
[1] https://github.com/ljharb/qs/security/advisories/GHSA-w7fw-mjwx-w883
[2] https://github.com/ljharb/qs/commit/f6a7abff1f13d644db9b05fe4f2c98ada6bf8482
Please adjust the affected versions in the BTS as needed.
Regards,
Salvatore
