Guessable CAPTCHA

The software 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 that 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 actors.

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.

See Also

Authentication Errors

Weaknesses in this category are related to authentication components of a system. Frequently these deal with the ability to verify that an entity is indeed who it clai...

Comprehensive CWE Dictionary

This view (slice) covers all the elements in CWE.

Weaknesses without Software Fault Patterns

CWE identifiers in this view are weaknesses that do not have associated Software Fault Patterns (SFPs), as covered by the CWE-888 view. As such, they represent gaps in...

Weaknesses Introduced During Implementation

This view (slice) lists weaknesses that can be introduced during implementation.

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