Discuz X5.0 up to 5.0 CAPTCHA Image Captcha

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
6.8$0-$5k0.00

Summaryinfo

A vulnerability categorized as critical has been discovered in Discuz X5.0 up to 5.0. This affects an unknown part of the component CAPTCHA Image Handler. Such manipulation leads to Captcha. This vulnerability is referenced as CVE-2026-49953. It is possible to launch the attack remotely. No exploit is available. Applying a patch is advised to resolve this issue.

Detailsinfo

A vulnerability was found in Discuz X5.0 up to 5.0 and classified as critical. Affected by this issue is an unknown functionality of the component CAPTCHA Image Handler. The manipulation with an unknown input leads to a captcha vulnerability. Using CWE to declare the problem leads to CWE-804. The product uses a CAPTCHA challenge, but the challenge can be guessed or automatically recognized by a non-human actor. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The weakness was published by Egidio Romano. The advisory is shared for download at karmainsecurity.com. This vulnerability is handled as CVE-2026-49953 since 06/02/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available.

Applying the patch 20260610 is able to eliminate this problem.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 6.9
VulDB Meta Temp Score: 6.8

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 6.5
CNA Vector (VulnCheck): 🔒

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Captcha
CWE: CWE-804 / CWE-287
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Patch: 20260610

Timelineinfo

06/02/2026 CVE reserved
06/16/2026 +14 days Advisory disclosed
06/16/2026 +0 days VulDB entry created
06/16/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: karmainsecurity.com
Researcher: Egidio Romano
Status: Confirmed

CVE: CVE-2026-49953 (🔒)
GCVE (CVE): GCVE-0-2026-49953
GCVE (VulDB): GCVE-100-371120

Entryinfo

Created: 06/16/2026 06:30
Changes: 06/16/2026 06:30 (76)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Do you need the next level of professionalism?

Upgrade your account now!