CVE-2021-43405
NVD-CWE-OtherPublished: November 5, 2021· Updated: Jun 17, 2026
Official 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).
Technical Analysis
CVE-2021-43405 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.
A proof-of-concept (PoC) exploit exists for CVE-2021-43405. While not yet confirmed in active campaigns, the availability of PoC code increases exploitation risk substantially.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (4)
Quick Facts
Related CVEs (NVD-CWE-Other)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-43405 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts