How severe is CVE-2021-4171?

CVE-2021-4171 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-2021-4171 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-4171?

CVE-2021-4171 affects Janeczku Calibre-web. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-4171?

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-2021-4171 published?

CVE-2021-4171 was published on 2022-01-17 and last updated on 2026-06-17.

CVE-2021-4171

CVE-2021-4171 is a critical-severity vulnerability in Janeczku Calibre-web 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-840.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 1% (69th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-840
Affected product: Janeczku Calibre-web
Published: 2022-01-17
Last modified: 2026-06-17

Description

calibre-web is vulnerable to Business Logic Errors

Frequently asked questions

What is CVE-2021-4171?: calibre-web is vulnerable to Business Logic Errors
How severe is CVE-2021-4171?: CVE-2021-4171 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-2021-4171 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-4171?: CVE-2021-4171 affects Janeczku Calibre-web. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-4171?: 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-2021-4171 published?: CVE-2021-4171 was published on 2022-01-17 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:janeczku:calibre-web:*:*:*:*:*:*:*:*

More vulnerabilities in Janeczku Calibre-web

CVE-2022-0939 — Critical (CVSS 9.9): Server-Side Request Forgery (SSRF) in GitHub repository janeczku/calibre-web prior to 0.6.18.
CVE-2022-0767 — Critical (CVSS 9.9): Server-Side Request Forgery (SSRF) in GitHub repository janeczku/calibre-web prior to 0.6.17.
CVE-2025-7404 — Critical (CVSS 9.8): Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') vulnerability in Calibre…
CVE-2023-2106 — Critical (CVSS 9.8): Weak Password Requirements in GitHub repository janeczku/calibre-web prior to 0.6.20.
CVE-2022-2525 — Critical (CVSS 9.8): Improper Restriction of Excessive Authentication Attempts in GitHub repository janeczku/calibre-web prior to 0.6.20.
CVE-2022-30765 — Critical (CVSS 9.8): Calibre-Web before 0.6.18 allows user table SQL Injection.

All CVEs affecting Janeczku Calibre-web →

Other CWE-840 vulnerabilities

CVE-2022-4719 — Critical (CVSS 9.8): Business Logic Errors in GitHub repository ikus060/rdiffweb prior to 2.5.5.
CVE-2022-3363 — Critical (CVSS 9.8): Business Logic Errors in GitHub repository ikus060/rdiffweb prior to 2.5.0a7.
CVE-2024-39671 — Critical (CVSS 9.3): Access control vulnerability in the security verification module. Impact: Successful exploitation of this vulnerability…
CVE-2024-54098 — High (CVSS 8.5): Service logic error vulnerability in the system service module Impact: Successful exploitation of this vulnerability…
CVE-2025-1908 — High (CVSS 7.7): An issue has been discovered in GitLab EE/CE that could allow an attacker to track users' browsing activities,…
CVE-2022-0524 — High (CVSS 7.5): Business Logic Errors in GitHub repository publify/publify prior to 9.2.7.

Browse all CWE-840 vulnerabilities →