| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| ### Summary
`qs.stringify` throws a `TypeError` when it serializes an object whose own `constructor` property has a truthy, non-callable `isBuffer` member. `utils.isBuffer` duck-types buffers by calling `obj.constructor.isBuffer(obj)` after checking only that the property is truthy, so a value such as `{ constructor: { isBuffer: "x" } }` makes the call throw `TypeError: obj.constructor.isBuffer is not a function`.
### Details
`lib/stringify.js:127` calls `utils.isBuffer` on every non-primitive value it serializes. `utils.isBuffer` (`lib/utils.js:332`) reads `obj.constructor.isBuffer` and invokes it without verifying that it is a function. `constructor` and `isBuffer` are ordinary property names, so any object carrying them as own properties reaches the unchecked call.
Such an object can be built from untrusted input. `qs.parse("x[constructor][isBuffer]=y", { plainObjects: true })` or `{ allowPrototypes: true }` keeps the `constructor` key as an own property (the default parse options drop it), and `JSON.parse("{\"a\":{\"constructor\":{\"isBuffer\":\"x\"}}}")` produces the same shape with no qs option involved. Express 4 with its default `query parser` setting and body-parser with `extended: true` both call `qs.parse` with `allowPrototypes: true`, so on those stacks `req.query` and `req.body` can carry the shape directly.
#### PoC
```js
var qs = require("qs");
qs.stringify(qs.parse("x[constructor][isBuffer]=y", { plainObjects: true }));
qs.stringify(JSON.parse("{\"a\":{\"constructor\":{\"isBuffer\":\"x\"}}}"));
// TypeError: obj.constructor.isBuffer is not a function
// at Object.isBuffer (lib/utils.js:332:78)
// at stringify (lib/stringify.js:127:45)
```
#### Fix
`lib/utils.js`, applied in e83d321 on `main` and released as v6.16.0:
```diff
- return !!(obj.constructor && obj.constructor.isBuffer && obj.constructor.isBuffer(obj));
+ return !!(obj.constructor && typeof obj.constructor.isBuffer === "function" && obj.constructor.isBuffer(obj));
```
Real `Buffer`, `safer-buffer`, and browserify `buffer` polyfill instances serialize exactly as before; only the throw is removed.
### Affected versions
`>=2.2.5 <6.16.0`, fixed in v6.16.0.
The unguarded duck-type was introduced in 3768a75 and first shipped in v2.2.5 (September 2014). v2.2.4 and earlier used `Buffer.isBuffer` and are not affected. Every release from v2.2.5 through v6.15.3 contains the unguarded call.
### Impact
An unauthenticated request can make any code path that re-serializes attacker-influenced data with `qs.stringify` (for example, rebuilding a query string from `req.query` for a redirect or an upstream request, or serializing a parsed JSON body) throw synchronously. In a typical Node.js HTTP framework the throw is caught by the framework error boundary and the affected request returns a 500; the process survives and other requests are unaffected. Where the call runs outside an error boundary, such as an `async` Express 4 handler (where the throw becomes an unhandled promise rejection) or a background job, the process exits, so the impact in that case depends on the application error handling rather than on qs. |
| ### Summary
When `qs.parse` is called with `comma: true` and `throwOnLimitExceeded: true`, a comma-separated value under a bracket-push key (`a[]=1,2,3,4`) is split into an array without being compared against `arrayLimit`, while the same value under a flat key (`a=1,2,3,4`), an indexed key (`a[0]=`), a nested key (`a[b]=`), or a dotted key (`a.b=` with `allowDots`) throws the documented `RangeError`. A single parameter such as `a[]=1,2,2,...` therefore produces an inner array of arbitrary length even though the caller opted into the hard limit. This is the `[]=` key form that the fix for CVE-2026-2391 (qs 6.14.2) did not cover.
### Details
In `lib/parse.js`, a comma-separated value under a `[]=` key is split and then wrapped as a single nested element (`val = [val]`, so that each `a[]=x,y` group counts as one element of the outer array). The `arrayLimit` check that 6.14.2 added for comma values runs after that wrap, so for `[]=` parts it only ever saw the wrapper of length 1. 6.15.3 added a pre-split comma count so that an oversized value throws before it is allocated, but gated it on an `isFlatArrayValue` flag that `parseValues` set to `false` for any part containing `[]=`, and did not pass it for object-valued input, so the gap remained.
#### PoC
```js
var qs = require('qs');
var options = { comma: true, arrayLimit: 3, throwOnLimitExceeded: true };
qs.parse('a=1,2,3,4', options); // RangeError: Array limit exceeded. Only 3 elements allowed in an array.
qs.parse('a[]=1,2,3,4', options); // { a: [ [ '1', '2', '3', '4' ] ] } (no throw)
qs.parse('a[]=' + '1,'.repeat(1000000) + '1', { comma: true, arrayLimit: 20, throwOnLimitExceeded: true });
// no throw; a 1,000,001-element inner array is allocated
```
#### Fix
`lib/parse.js`, applied in 8859c37 on `main` and released as v6.16.0: the `isFlatArrayValue` gate is removed, so every comma-split value is counted against `arrayLimit` before splitting regardless of key form. An in-limit group under `a[]=` still counts as one element of the outer array, and the default (`throwOnLimitExceeded: false`) path is unchanged.
### Affected versions
`>=6.14.2 <6.16.0`, fixed in v6.16.0.
v6.14.2 introduced `arrayLimit` enforcement for comma values (the fix for CVE-2026-2391) but only for values not under a `[]=` key, and every release from v6.14.2 through v6.15.3 has the same gap. v6.14.0 and v6.14.1, where `throwOnLimitExceeded` exists but does not apply to any comma form, are covered by CVE-2026-2391 rather than this record. Earlier lines (6.7.x through 6.13.x) have `comma` but no `throwOnLimitExceeded`, so there is no hard cap on any comma path to bypass; releases before 6.7.0 have no `comma` option.
### Impact
An unauthenticated attacker who can reach an application that parses untrusted query strings or urlencoded bodies with both `comma: true` and `throwOnLimitExceeded: true` (both non-default) can bypass the configured limit with a single `a[]=` parameter and force the parser to allocate an array proportional to the request size. The cost is strictly linear in the attacker-supplied bytes (about 0.1 microseconds and 6 to 7 retained bytes per input byte; the same out-of-memory threshold as the documented default `throwOnLimitExceeded: false` path), so a transport-layer request or body size limit bounds it completely (and node's default maximum HTTP header size of 16 KB already bounds the request line, so multi-megabyte payloads need a body parser). The impact is that an opt-in hard limit fails open on one key spelling, not unbounded allocation from a small input. |
| The Frontend Admin by DynamiApps WordPress plugin before 3.29.11 does not perform a capability check on one of its AJAX actions, allowing any authenticated user, such as a subscriber, to delete arbitrary membership plans. |
| The MasterStudy LMS WordPress Plugin WordPress plugin before 3.7.43 does not validate a redirect parameter supplied during user registration before using it, allowing unauthenticated attackers to redirect users to arbitrary external URLs. |
| The MasterStudy LMS WordPress Plugin WordPress plugin before 3.7.42 does not correctly restrict access to order information, allowing any user with the instructor role to read other users' order billing details, including name, email address, phone number and postal address, by enumerating order IDs. |
| The MasterStudy LMS WordPress Plugin WordPress plugin before 3.7.40 does not verify the amount, receiver, currency or status of a payment notification before marking the corresponding order completed, allowing unauthenticated users to complete full-price orders and gain access to paid content by paying only a token amount. |
| The WP Ultimate CSV Importer WordPress plugin before 9.0 does not properly sanitise and escape imported field values before using them in a SQL statement, which could allow high privilege users such as admin to perform SQL injection attacks. |
| The Stripe Payment Forms by WP Full Pay WordPress plugin before 8.5.5 does not verify that a subscription belongs to the customer bound to the requesting customer-portal session before cancelling it, allowing a user with a confirmed portal session to cancel subscriptions belonging to other customers.
Exploitation requires the attacker to know the target subscription's identifier, which is high-entropy and not enumerable through the Stripe Payment Forms by WP Full Pay WordPress plugin before 8.5.5. |
| The Rank Math SEO WordPress plugin before 1.0.277 does not check that the user requesting an automated SEO fix holds the capability WordPress itself requires for the settings being changed, allowing users with the Editor role to modify site-wide core WordPress settings that are reserved to administrators. |
| The Booking for Appointments and Events Calendar WordPress plugin before 2.4.9 does not check that a user holds the required capability before letting them change an appointment's status, allowing customers to set arbitrary statuses on appointments they are booked on, including approving their own bookings that were left awaiting approval and overwriting another customer's booking status on a shared appointment. |
| The 爱采集数据采集和发布插件 WordPress plugin through 1.0.0 does not require a per-install secret for one of its unauthenticated endpoints, relying on a hardcoded default, and does not validate the URLs or destination paths it is given, allowing unauthenticated attackers to read arbitrary files from the server, force it to issue arbitrary requests and retrieve the responses, and write attacker-supplied content outside the uploads directory. |
| The HEL Online Classroom: AI-powered Online Classrooms WordPress plugin through 1.0.3 does not perform authorisation checks on its REST API routes and does not consistently enforce the per-class access code, allowing unauthenticated users to obtain a signed meeting join link for any classroom, including one protected by an access code, and to join it with moderator privileges. |
| The HEL Online Classroom: AI-powered Online Classrooms WordPress plugin through 1.0.3 does not have any authorisation or authentication check when saving its settings, allowing unauthenticated users to overwrite them and repoint every online classroom, along with the shared secret those sessions are signed with, at infrastructure of their choosing. |
| The HEL Online Classroom: AI-powered Online Classrooms WordPress plugin through 1.0.3 does not perform any authorisation check on one of its REST API routes, allowing unauthenticated users to retrieve its stored settings, including the shared secret used to sign API requests to the connected BigBlueButton server. |
| The Appointment Booking Calendar Plugin and Scheduling Plugin WordPress plugin before 1.6.3 does not verify the amount actually paid against the server-side price staged for a booking when confirming an online payment, allowing unauthenticated users to have a paid appointment approved for a fraction of its price. |
| The User Profile Builder WordPress plugin before 4.0.1 does not properly restrict its front-end file upload feature, granting unauthenticated visitors capabilities reserved to privileged roles. This allows them to list the site's media library and to modify unpublished posts, pages and media items belonging to other users. |
| The User Profile Builder WordPress plugin before 4.0.1 does not validate the type of data being deserialized when importing a configuration file, allowing high privilege users such as administrators to conduct PHP Object Injection. The affected feature is a free add-on which is disabled by default, and no POP chain is present in the User Profile Builder WordPress plugin before 4.0.1 itself, so further impact requires a suitable gadget from another installed User Profile Builder WordPress plugin before 4.0.1 or . |
| The User Profile Builder WordPress plugin before 4.0.1 does not escape the output of one of its optional shortcodes, allowing users with a role as low as contributor to perform Stored Cross-Site Scripting attacks against any user viewing the affected content, including administrators. The shortcode is not enabled by default. |
| Access of resource using incompatible type ('type confusion') in Microsoft Edge (Chromium-based) allows an unauthorized attacker to execute code over a network. |
| Improper neutralization of parameter/argument delimiters in Microsoft Edge (Chromium-based) allows an unauthorized attacker to execute code over a network. |
