Guessable CAPTCHA

Opis

The product uses a CAPTCHA challenge, but the challenge can be guessed or automatically recognized by a non-human actor.

An automated attacker could bypass the intended protection of the CAPTCHA challenge and perform actions at a higher frequency than humanly possible, such as launching spam attacks.

There can be several different causes of a guessable CAPTCHA:

- An audio or visual image that does not have sufficient distortion from the unobfuscated source image.

- A question is generated with a format that can be automatically recognized, such as a math question.

- A question for which the number of possible answers is limited, such as birth years or favorite sports teams.

- A general-knowledge or trivia question for which the answer can be accessed using a data base, such as country capitals or popular entertainers.

- Other data associated with the CAPTCHA may provide hints about its contents, such as an image whose filename contains the word that is used in the CAPTCHA.

Skutki

• Access Control, Other

  Bypass Protection Mechanism; Other

  When authorization, authentication, or another protection mechanism relies on CAPTCHA entities to ensure that only human actors can access certain functionality, then an automated attacker such as a bot may access the restricted functionality by guessing the CAPTCHA.

Przykłady podatności

• CVE-2022-4036 Chain: appointment booking app uses a weak hash (CWE-328) for generating a CAPTCHA, making it guessable (CWE-804)

Słabość nadrzędna

• CWE-863 Incorrect Authorization
• CWE-1390 Weak Authentication

Kiedy powstaje

• Architecture and Design
• Implementation

Dotyczy

Not Language-Specific, Web Server

Źródła

1. Insufficient Anti-automation — Web Application Security Consortium