CVE-2026-49953 Details
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.
A CAPTCHA bypass vulnerability has been identified in Discuz! X5.0, specifically in releases from 20260320 to 20260610. This vulnerability allows unauthenticated remote attackers to circumvent CAPTCHA challenges by exploiting the simplicity and predictability of the generated images. Attackers can collect CAPTCHA samples, train a custom optical character recognition (OCR) model, and reliably predict the challenge text. This bypasses protections on login, registration, and other functionalities, facilitating automated abuse.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jun 15, 2026CISA-ADP
Assessed Jun 15, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| http://seclists.org/fulldisclosure/2026/Jun/4 | CVE | |
| https://karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rce | [email protected] | BundleExploitRemedyTechnical Analysis |
| https://karmainsecurity.com/KIS-2026-10 | [email protected] | AdvisoryExploitRemedy |
| https://www.vulncheck.com/advisories/discuz-x5-0-captcha-bypass-via-predictable-character-set | [email protected] | Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-804 | Guessable CAPTCHA | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Discuz! | >= 20260320, <= 20260610 |
CPE
Remediation
| |
Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Jun 16, 2026 | CVE Modified | CVE |
| Jun 15, 2026 | CVE Modified | [email protected] |
| Jun 15, 2026 | New CVE Received | [email protected] |