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CVE-2021-43405

58
FAUCET Score

CVE-2021-43405 is a high-severity vulnerability affecting FusionPBX versions prior to 4.5.30, stemming from insufficient input validation in the fax_extension field, which allows risky characters. With a CVSS score of 8.8, this flaw enables authenticated attackers to achieve high impact on confidentiality, integrity, and availability. While not listed on the KEV catalog, an authenticated Remote Code Execution (RCE) exploit for FusionPBX 4.5.29 is publicly available on ExploitDB, though there is no evidence of active exploitation or significant community discussion.

Impacted Technologies

VendorProductVersion(s)CPE
< 4.5.30CPE matchmatch criteria
cpe:2.3:a:fusionpbx:fusionpbx:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.8HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
35.63%
Probability of exploitation in next 30 days
EPSS Percentile
98.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
ExploitDB: EDB-50505 · Nov 8, 2021
This CVE's current EPSS score of 0.3563 is in the 98th percentile among its peer group of 17,844 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

packetstormsecurity.com / files/164795/FusionPBX-4.5.29-Remote-Code-Execution.html
ExploitThird Party Advisory
github.com / fusionpbx/fusionpbx/commit/2d2869c1a1e874c46a8c3c5475614ce769bbbd59
PatchThird Party Advisory