How severe is CVE-2021-3663?

CVE-2021-3663 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-3663 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3663?

CVE-2021-3663 affects Firefly-iii Firefly Iii. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3663?

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

When was CVE-2021-3663 published?

CVE-2021-3663 was published on 2021-07-25 and last updated on 2026-06-17.

CVE-2021-3663

CVE-2021-3663 is a high-severity vulnerability in Firefly-iii Firefly Iii with a CVSS 3.x base score of 7.5. 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-307.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (49th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-307
Affected product: Firefly-iii Firefly Iii
Published: 2021-07-25
Last modified: 2026-06-17

Description

firefly-iii is vulnerable to Improper Restriction of Excessive Authentication Attempts

Frequently asked questions

What is CVE-2021-3663?: firefly-iii is vulnerable to Improper Restriction of Excessive Authentication Attempts
How severe is CVE-2021-3663?: CVE-2021-3663 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-3663 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3663?: CVE-2021-3663 affects Firefly-iii Firefly Iii. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3663?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-3663 published?: CVE-2021-3663 was published on 2021-07-25 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:firefly-iii:firefly_iii:*:*:*:*:*:*:*:*

More vulnerabilities in Firefly-iii Firefly Iii

CVE-2023-1788 — Critical (CVSS 9.8): Insufficient Session Expiration in GitHub repository firefly-iii/firefly-iii prior to 6.
CVE-2023-1789 — Critical (CVSS 9.8): Improper Input Validation in GitHub repository firefly-iii/firefly-iii prior to 6.0.0.
CVE-2021-3901 — High (CVSS 8.8): firefly-iii is vulnerable to Cross-Site Request Forgery (CSRF)
CVE-2021-3846 — High (CVSS 8.8): firefly-iii is vulnerable to Unrestricted Upload of File with Dangerous Type
CVE-2021-3819 — High (CVSS 8.8): firefly-iii is vulnerable to Cross-Site Request Forgery (CSRF)
CVE-2023-0298 — Medium (CVSS 6.5): Incorrect Authorization in GitHub repository firefly-iii/firefly-iii prior to 5.8.0.

All CVEs affecting Firefly-iii Firefly Iii →

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