How severe is CVE-2021-3990?

CVE-2021-3990 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-3990 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3990?

CVE-2021-3990 affects Showdoc. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3990?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-3990 published?

CVE-2021-3990 was published on 2021-12-01 and last updated on 2026-06-17.

CVE-2021-3990

CVE-2021-3990 is a medium-severity vulnerability in Showdoc with a CVSS 3.x base score of 6.5. 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-338.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (54th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-338
Affected product: Showdoc
Published: 2021-12-01
Last modified: 2026-06-17

Description

showdoc is vulnerable to Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

Frequently asked questions

What is CVE-2021-3990?: showdoc is vulnerable to Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
How severe is CVE-2021-3990?: CVE-2021-3990 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-3990 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3990?: CVE-2021-3990 affects Showdoc. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3990?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-3990 published?: CVE-2021-3990 was published on 2021-12-01 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:showdoc:showdoc:*:*:*:*:*:*:*:*

More vulnerabilities in Showdoc

CVE-2022-0362 — Critical (CVSS 9.8): SQL Injection in Packagist showdoc/showdoc prior to 2.10.3.
CVE-2021-41745 — Critical (CVSS 9.8): ShowDoc 2.8.3 ihas a file upload vulnerability, where attackers can use the vulnerability to obtain server permissions.
CVE-2021-36440 — Critical (CVSS 9.8): Unrestricted File Upload in ShowDoc v2.9.5 allows remote attackers to execute arbitrary code via the 'file_url'…
CVE-2021-4168 — High (CVSS 8.8): showdoc is vulnerable to Cross-Site Request Forgery (CSRF)
CVE-2021-4017 — High (CVSS 8.8): showdoc is vulnerable to Cross-Site Request Forgery (CSRF)
CVE-2022-0409 — High (CVSS 7.8): Unrestricted Upload of File with Dangerous Type in Packagist showdoc/showdoc prior to 2.10.2.

All CVEs affecting Showdoc →

Other CWE-338 vulnerabilities

CVE-2026-56141 — Critical (CVSS 9.8): In JetBrains Hub before 2026.1.13757, 2025.3.148033, 2025.2.148048, 2025.1.148120, 2024.3.148430, 2024.2.148429 account…
CVE-2026-3256 — Critical (CVSS 9.8): HTTP::Session versions before 0.54 for Perl defaults to using insecurely generated session ids. HTTP::Session defaults…
CVE-2025-15604 — Critical (CVSS 9.8): Amon2 versions before 6.17 for Perl use an insecure random_string implementation for security functions. In versions…
CVE-2025-40926 — Critical (CVSS 9.8): Plack::Middleware::Session::Simple versions before 0.05 for Perl generates session ids insecurely. The default session…
CVE-2026-2439 — Critical (CVSS 9.8): Concierge::Sessions versions from 0.8.1 before 0.8.5 for Perl generate insecure session ids. The generate_session_id…
CVE-2025-15578 — Critical (CVSS 9.8): Maypole versions from 2.10 through 2.13 for Perl generates session ids insecurely. The session id is seeded with the…

Browse all CWE-338 vulnerabilities →