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Advisories

Discuz! X5.0 CAPTCHA Bypass via Predictable Character Set

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severity
medium
date
Affecting

  • Discuz! X5.0 releases 20260320 <= 20260610

  • An affected version range remains undefined

CWE
  • CWE-804 Guessable CAPTCHA
CVSS
6.9
CVSS V4 Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Credit
Egidio Romano
Description
Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that allows unauthenticated remote attackers to defeat challenge controls by exploiting limited complexity and predictable character sets in generated CAPTCHA images. Attackers can train a custom optical character recognition model against collected CAPTCHA samples to reliably predict challenge text, bypassing protections on login, registration, and other functionality from automated abuse.

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