Medium severity6.5NVD Advisory· Published Jun 15, 2026· Updated Jun 16, 2026

CVE-2026-49953

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.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected products

Discuz/Discuz\!llm-fuzzy
Range: >=20260320, <=20260610

Patches

Vulnerability mechanics

References

seclists.org/fulldisclosure/2026/Jun/4nvd
karmainsecurity.com/KIS-2026-10nvd
karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rcenvd
www.vulncheck.com/advisories/discuz-x5-0-captcha-bypass-via-predictable-character-setnvd

News mentions

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