TI-2026-36796 Aliases CVE-2026-49953 GHSA-p3qj-vw7q-v9pc

Discuz! X5.0 CAPTCHA Bypass via Predictable Character Set

HIGH 70CWE-804Published 2026-06-15 · Updated 2026-07-28

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: —
Confidentiality · integrity · availability: Low · Low · None
Fix status: No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00359 29th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by the CNA

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Discuz!	Discuz! X5.0	20260320 – 20260610	—	No fix listed	CNA

Discuz! X5.0 VendorDiscuz! Affected 20260320 – 20260610 Fixed in — No fix listed CNA

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2026-49953
2026-10-03 Alias added: GHSA-p3qj-vw7q-v9pc

References

Exploit 1

https://karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rce

Other 1

https://karmainsecurity.com/KIS-2026-10

TI-2026-36795 Discuz! X5.0 Authentication Bypass via dbbak.php Encryption Oracle CVSS 4.0CRITICAL 9.3
TI-2026-36797 Discuz! X5.0 Local File Inclusion via enable_disable.php Plugin Directory CVSS 4.0HIGH 8.6
TI-2024-20381 Reflected Cross-Site Scripting (XSS) vulnerability in Discuz! version X3.4 20220811… CVSS 3.1HIGH 7.1
TI-2022-22486 Cross site scripting (XSS) vulnerability in DiscuzX 3.4 allows attackers to execute… CVSS 3.1MEDIUM 6.1
TI-2018-03910 Discuz! DiscuzX X3.4 allows remote attackers to bypass intended access restrictions via… CVSS 3.0CRITICAL 9.8
TI-2018-03813 Discuz! DiscuzX X3.4 allows remote authenticated users to bypass intended… CVSS 3.0HIGH 8.8

See all 14 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences