CVE-2026-49953 MEDIUM

CVE-2026-49953: Discuz! X5.0 CAPTCHA Bypass via Predictable Character Set

Vendor Discuz!
Product Discuz! X5.0
Weakness CWE-804
Published June 15, 2026
Last update June 16, 2026
View on NVD All CVEs

CVSS base score

6.9/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS 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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

June 15, 2026 CVE published
June 16, 2026 Record updated