What is CVE-2021-3663?

CVE-2021-3663 is a high-severity vulnerability in Firefly-Iii Firefly Iii, classified under Improper Restriction of Excessive Authentication Attempts. CVSS score: 7.5/10. Published 2021-07-25.

How severe is CVE-2021-3663?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Firefly-Iii Firefly Iii

CVE-2021-3663

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

Published 2021-07-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.007 (51.8th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 51.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Firefly-Iii Firefly Iii
Firefly-Iii Firefly-Iii/firefly-Iii — versions unspecified

Weakness classification (CWE)

CWE-307 — Improper Restriction of Excessive Authentication Attempts

References

huntr.dev/bounties/497bdf6d-7dba-49c3-8011-1c64dfbb3380 (Exploit, Third Party Advisory)
github.com/firefly-iii/firefly-iii/commit/afc9f4b7ebc8a240c85864a6e1abda62bfeef… (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-3663?: CVE-2021-3663 is a high-severity vulnerability in Firefly-Iii Firefly Iii, classified under Improper Restriction of Excessive Authentication Attempts. CVSS score: 7.5/10. Published 2021-07-25.
How severe is CVE-2021-3663?: High severity. CVSS v3 base score is 7.5 out of 10.