What is CVE-2021-43406?

CVE-2021-43406 is a high-severity vulnerability in Fusionpbx, classified under Improper Input Validation. CVSS score: 8.8/10. Published 2021-11-05.

How severe is CVE-2021-43406?

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

Improper input validation in Fusionpbx

CVE-2021-43406

An issue was discovered in FusionPBX before 4.5.30. The fax_post_size may have risky characters (it is not constrained to preset values).

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2021-11-05 · last modified 2026-06-17.

CVSS v3 metric

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

EPSS exploit prediction

EPSS: 0.010 (60.5th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 60th percentile — 60.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000

Affected products

Fusionpbx

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

github.com/fusionpbx/fusionpbx/commit/0377b2152c0e59c8f35297f9a9b6ee335a62d963 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-43406?: CVE-2021-43406 is a high-severity vulnerability in Fusionpbx, classified under Improper Input Validation. CVSS score: 8.8/10. Published 2021-11-05.
How severe is CVE-2021-43406?: High severity. CVSS v3 base score is 8.8 out of 10.