CVE-2026-49953

MEDIUM EPSS 27.8%
Published Jun 15, 20262w ago · Modified Jun 17, 20262w ago
6.9 CVSS 4.0
Medium
Find Similar
Published Jun 15, 2026 2w ago
Last Modified Jun 17, 2026 2w ago

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.

CVSS Details

Base Score
6.9
Exploitability
—
Impact
—
Vector string
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
27.8% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-804

References 4

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

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.