How severe is CVE-2018-18531?

CVE-2018-18531 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2018-18531 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-18531?

CVE-2018-18531 affects Kaptcha Project Kaptcha. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2018-18531?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2018-18531 published?

CVE-2018-18531 was published on 2018-10-19 and last updated on 2026-06-17.

CVE-2018-18531

CVE-2018-18531 is a critical-severity vulnerability in Kaptcha Project Kaptcha with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-330.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 5.0
EPSS exploit prediction: 1% (71st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-330
Affected product: Kaptcha Project Kaptcha
Published: 2018-10-19
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2018-18531?: 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.
How severe is CVE-2018-18531?: CVE-2018-18531 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2018-18531 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-18531?: CVE-2018-18531 affects Kaptcha Project Kaptcha. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2018-18531?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2018-18531 published?: CVE-2018-18531 was published on 2018-10-19 and last updated on 2026-06-17.

References

https://github.com/penggle/kaptcha/issues/3

Affected products (1)

cpe:2.3:a:kaptcha_project:kaptcha:2.3.2:*:*:*:*:*:*:*

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