How severe is CVE-2021-43405?

CVE-2021-43405 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-43405 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 36% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43405?

CVE-2021-43405 affects Fusionpbx. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43405?

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-2021-43405 published?

CVE-2021-43405 was published on 2021-11-05 and last updated on 2026-06-17.

CVE-2021-43405

CVE-2021-43405 is a high-severity vulnerability in Fusionpbx with a CVSS 3.x base score of 8.8. Its EPSS exploit-prediction score of 36% places it in the 98th percentile, indicating an elevated likelihood of exploitation.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 6.5
EPSS exploit prediction: 36% (98th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Fusionpbx
Published: 2021-11-05
Last modified: 2026-06-17

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).

Frequently asked questions

What is CVE-2021-43405?: An issue was discovered in FusionPBX before 4.5.30. The fax_extension may have risky characters (it is not constrained to be numeric).
How severe is CVE-2021-43405?: CVE-2021-43405 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43405 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 36% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43405?: CVE-2021-43405 affects Fusionpbx. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43405?: 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-2021-43405 published?: CVE-2021-43405 was published on 2021-11-05 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:fusionpbx:fusionpbx:*:*:*:*:*:*:*:*

More vulnerabilities in Fusionpbx

CVE-2022-35153 — Critical (CVSS 9.8): FusionPBX 5.0.1 was discovered to contain a command injection vulnerability via /fax/fax_send.php.
CVE-2022-28055 — Critical (CVSS 9.8): Fusionpbx v4.4 and below contains a command injection vulnerability via the download email logs function.
CVE-2021-43406 — High (CVSS 8.8): An issue was discovered in FusionPBX before 4.5.30. The fax_post_size may have risky characters (it is not constrained…
CVE-2021-43404 — High (CVSS 8.8): An issue was discovered in FusionPBX before 4.5.30. The FAX file name may have risky characters.
CVE-2019-16964 — High (CVSS 8.8): app/call_centers/cmd.php in the Call Center Queue Module in FusionPBX up to 4.5.7 suffers from a command injection…
CVE-2019-16980 — High (CVSS 8.8): In FusionPBX up to v4.5.7, the file app\call_broadcast\call_broadcast_edit.php uses an unsanitized "id" variable coming…

All CVEs affecting Fusionpbx →