Which products and versions are affected by CVE-2021-43405?

Affected: Fusionpbx. The full list is in the CVE brief.

Is CVE-2021-43405 being exploited in the wild?

It is not listed in any known-exploited vulnerabilities catalog.

Is CVE-2021-43405 in the CISA KEV catalog?

No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

Is there a public exploit for CVE-2021-43405?

Public exploit code is available.

Is there a fix for CVE-2021-43405?

Fixed versions are available, including Fusionpbx 4.5.30.

How urgently should CVE-2021-43405 be patched?

Brandefense priority: patch immediately, because public exploit code exists for a high-severity flaw.

Request A Demo

WatchlistHigh

CVE-2021-43405Fusionpbx Vulnerability

The fax_extension may have risky characters (it is not constrained to be numeric).

Published Nov 5, 2021 · Updated Jul 8, 2026

Key Facts

Patch immediately

CVE-2021-43405 is a high-severity vulnerability (CVSS 8.8 v3.1) affecting Fusionpbx.
It is not listed in any known-exploited vulnerabilities catalog. Public exploit code is available.
EPSS estimates a 36% probability of exploitation in the next 30 days.
Fixed versions are available, including Fusionpbx 4.5.30.
Brandefense priority: patch immediately, because public exploit code exists for a high-severity flaw.

Scores

CVSS v3.1

8.8

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS (30-day exploit likelihood)

36%

Higher than 98.4% of all scored CVEs

Exploit maturity

Proof of concept

ATLAS score

39/100

Publication score, see How it works

Exploitation Verdict

KEV listed

Not listed

Federal due date

None

No federal due date

Ransomware use

Not reported

Attributed actors

None named

Exploit & Defence Guidance

Exploit maturity

Proof of concept

Public exploit code

Proof-of-concept links

In-the-wild evidence

Reports of active use

Advisories And Exploit References

patchhttps://github.com/fusionpbx/fusionpbx/commit/2d2869c1a1e874c46a8c3c5475614ce769bbbd59

Description

An issue was discovered in FusionPBX before 4.5.30. The fax_extension may have risky characters (it is not constrained to be numeric).

Affected Products

1 affected entries in total

Product	Affected versions	Fixed in
FusionpbxFusionpbx	See advisory	4.5.30

Patched Releases

Fusionpbx

4.5.30

Timeline

Publicly disclosed
Nov 5, 2021
Last updated
Jul 8, 2026

References

patchgithub.com · 2d2869c
exploitpacketstormsecurity.com · FusionPBX-4.5.29-Remote-Code-Execution.html
exploitExploitDB-50505

FAQ

Common Questions.

An issue was discovered in FusionPBX before 4.5.30.
Affected: Fusionpbx. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
Public exploit code is available.
Fixed versions are available, including Fusionpbx 4.5.30.
Brandefense priority: patch immediately, because public exploit code exists for a high-severity flaw.

Is CVE-2021-43405 On Your Attack Surface?

Brandefense matches it against the products discovered on your perimeter and opens a finding the day a CVE like this is listed.