EUVD-2026-292671

fkie_cve-2026-40935

WWBN AVideo is an open source video platform. In versions 29.0 and prior, `objects/getCaptcha.php` accepts the CAPTCHA length (`ql`) directly from the query string with no clamping or sanitization, letting any unauthenticated client force the server to generate a 1-character CAPTCHA word. Combined with a case-insensitive `strcasecmp` comparison over a ~33-character alphabet and the fact that failed validations do NOT consume the stored session token, an attacker can trivially brute-force the CAPTCHA on any endpoint that relies on `Captcha::validation()` (user registration, password recovery, contact form, etc.) in at most ~33 requests per session. Commit bf1c76989e6a9054be4f0eb009d68f0f2464b453 contains a fix.

GHSA-hg7g-56h5-5pqr — CAPTCHA Bypass in WWBN/AVideo via Attacker-Controlled Length Parameter and Missing Token Invalidation on Failure

Affected: Packagist: wwbn/avideo

## Summary

`objects/getCaptcha.php` accepts the CAPTCHA length (`ql`) directly from the query string with no clamping or sanitization, letting any unauthenticated client force the server to generate a 1-character CAPTCHA word. Combined with a case-insensitive `strcasecmp` comparison over a ~33-character alphabet and the fact that failed validations do NOT consume the stored session token, an attacker can trivially brute-force the CAPTCHA on any endpoint that relies on `Captcha::validation()` (user registration, password recovery, contact form, etc.) in at most ~33 requests per session.

## Details

Three cooperating flaws in `objects/getCaptcha.php` and `objects/captcha.php` reduce CAPTCHA protection to a deterministic bypass.

### 1. External control of CAPTCHA strength (`objects/getCaptcha.php:7`)

```php $largura = empty($_GET['l']) ? 120 : $_GET['l']; $altura = empty($_GET['a']) ? 40 : $_GET['a']; $tamanho_fonte = empty($_GET['tf']) ? 18 : $_GET['tf']; $quantidade_letras = empty($_GET['ql']) ? 5 : $_GET['ql']; // attacker-controlled

$capcha = new Captcha($largura, $altura, $tamanho_fonte, $quantidade_letras); $capcha->getCaptchaImage(); ```

There is no minimum, no type-check, and no clamping. Requesting `/objects/getCaptcha.php?ql=1` causes the server to generate a single-character word and save it to the attacker's own PHP session.

### 2. Small alphabet stored in the session (`objects/captcha.php:33-39`)

```php $letters = 'AaBbCcDdEeFfGgHhIiJjKk…

Most recent entries from all

EUVD-2026-292671

fkie_cve-2026-40935

GHSA-hg7g-56h5-5pqr — CAPTCHA Bypass in WWBN/AVideo via Attacker-Controlled Length Parameter and Missing Token Invalidation on Failure