kaptcha 2.3.2 Captcha DefaultTextCreator.java Random random values

Summaryinfo

A vulnerability identified as problematic has been detected in kaptcha 2.3.2. This impacts the function random of the file text/impl/DefaultTextCreator.java of the component Captcha. This manipulation causes random values. This vulnerability is tracked as CVE-2018-18531. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability was found in kaptcha 2.3.2. It has been declared as critical. Affected by this vulnerability is the function Random of the file text/impl/DefaultTextCreator.java of the component Captcha. The manipulation with an unknown input leads to a random values vulnerability. The CWE definition for the vulnerability is CWE-330. The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

text/impl/DefaultTextCreator.java, text/impl/ChineseTextProducer.java, and text/impl/FiveLetterFirstNameTextCreator.java in kaptcha 2.3.2 use the Random (rather than SecureRandom) function for generating CAPTCHA values, which makes it easier for remote attackers to bypass intended access restrictions via a brute-force approach.

The bug was discovered 10/17/2018. The weakness was disclosed 10/19/2018 (Website). It is possible to read the advisory at github.com. This vulnerability is known as CVE-2018-18531 since 10/19/2018. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1600.001 according to MITRE ATT&CK.

The vulnerability was handled as a non-public zero-day exploit for at least 2 days. During that time the estimated underground price was around $0-$5k.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

• kaptcha

Version

• 2.3.2

CPE 2.3info

• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍

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• Submit #XXXXXX: Xxxxxxxxxx Xxxxxxxx ≤ Xx.x.x Xxxxxxx Xxxxx-xxxxx (by ez-lbz)

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