# CVE-2026-49953

## Summary

- **CVE ID:** CVE-2026-49953
- **Severity:** MEDIUM
- **CVSS Score:** 6.9 (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)
- **CWE:** CWE-804
- **Published:** Jun 15, 2026
- **Last Modified:** Jul 28, 2026

## Description

Discuz! X5.0 releases 20260320 through 20260501 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.

## Affected Products

- Discuz! — Discuz! X5.0 (20260320)

## References

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

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.36%
- **EPSS Percentile:** 29.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._