What is CVE-2021-3901?

CVE-2021-3901 is a high-severity vulnerability in Firefly-Iii Firefly Iii, classified under Cross-Site Request Forgery (CSRF). CVSS score: 8.8/10. Published 2021-10-27.

How severe is CVE-2021-3901?

High severity. CVSS v3 base score is 8.8 out of 10.

CSRF in Firefly-Iii Firefly Iii

CVE-2021-3901

firefly-iii is vulnerable to Cross-Site Request Forgery (CSRF)

Vulnerability class: CSRF (Cross-Site Request Forgery)

Published 2021-10-27 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.006 (44.4th percentile), scored 2026-10-07.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 44.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000

Affected products

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

Weakness classification (CWE)

CWE-352 — Cross-Site Request Forgery (CSRF)

References

huntr.dev/bounties/62508fdc-c26b-4312-bf75-fd3a3f997464 (Exploit, Patch, Third Party Advisory, Issue Tracking)
github.com/firefly-iii/firefly-iii/commit/b42d8d1e305cad70d9b83b33cd8e0d7a4b206… (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-3901?: CVE-2021-3901 is a high-severity vulnerability in Firefly-Iii Firefly Iii, classified under Cross-Site Request Forgery (CSRF). CVSS score: 8.8/10. Published 2021-10-27.
How severe is CVE-2021-3901?: High severity. CVSS v3 base score is 8.8 out of 10.