CVE-2026-49953

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.

CVSS v3 6.5 MEDIUM

6.5^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 3.9 / Impact : 2.5

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://karmainsecurity.com/KIS-2026-10
https://karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rce
https://www.vulncheck.com/advisories/discuz-x5-0-captcha-bypass-via-predictable-character-set
http://seclists.org/fulldisclosure/2026/Jun/4

Configurations

No configuration.

History

No history.

Information

Published : 2026-06-15 20:16

Updated : 2026-06-17 10:55

NVD link : CVE-2026-49953

Mitre link : CVE-2026-49953

CVE.ORG link : CVE-2026-49953

JSON object : View

Products Affected

No product.

CWE

CWE-804

Guessable CAPTCHA

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