Vulnerability report

Exploited in the wild High confidence Not in CISA KEV

CVE-2021-45461

Rest Phone Apps

FreePBX / Rest Phone Apps

Watch CVE-2021-45461 Browse KEV feed
Severity
CVSS 9.8 · Critical
Confidence
High
Exploit status
Exploited in the wild
EPSS
21.7%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-45461 is an unauthenticated vulnerability affecting FreePBX Rest Phone Apps. FreePBX, when restapps (aka Rest Phone Apps) 15.0.19.87, 15.0.19.88, 16.0.18.40, or 16.0.18.41 is installed, allows remote...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is high. Also confirmed by third-party sources.

Who is affected?

FreePBX / Rest Phone Apps.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Rest Phone Apps

FreePBX, when restapps (aka Rest Phone Apps) 15.0.19.87, 15.0.19.88, 16.0.18.40, or 16.0.18.41 is installed, allows remote attackers to execute arbitrary code, as exploited in the wild in December 2021.

The fixed versions are 15.0.20 and 16.0.19.

Published
22 Dec 2021
Exploitation Reported
22 Dec 2021
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CVE

Recorded 22 Dec 2021

A trusted third party reported exploitation.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

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Source Added
CVE First 2021-12-22 18:25 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.8 Critical

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

21.7%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

All CVSS Scores

CVSS v3.1 9.8 Critical

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

CVSS v2.0 7.5 High

AV:N/AC:L/Au:N/C:P/I:P/A:P

Timeline

From disclosure to observed exploitation

  1. 18:25 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  2. 18:25 UTC

    CVE published

    Vulnerability disclosed publicly

  3. 00:00 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2021-45461

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2021-45461",
  "confidence": "High",
  "cvss_score": 9.8,
  "cvss_estimated": false,
  "epss_score": 0.21657,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}