CVE-2025-66039: Sangoma FreePBX Auth Bypass Vulnerability

CVE-2025-66039 Overview

CVE-2025-66039 is a critical authentication bypass vulnerability affecting the FreePBX Endpoint Manager module, which is used for managing telephony endpoints in FreePBX systems. The vulnerability allows attackers to completely bypass authentication when the system's authentication type is configured as "webserver." By providing an Authorization header with an arbitrary value, an attacker can associate a session with any target user without providing valid credentials, effectively gaining unauthorized access to the FreePBX administration interface.

Critical Impact
This authentication bypass vulnerability allows unauthenticated remote attackers to gain full access to FreePBX telephony management systems, potentially enabling call interception, configuration changes, and complete system compromise.

Affected Products

Sangoma FreePBX versions prior to 16.0.44
Sangoma FreePBX versions prior to 17.0.23
FreePBX Endpoint Manager module with "webserver" authentication type enabled

Discovery Timeline

2025-12-09 - CVE-2025-66039 published to NVD
2026-02-02 - Last updated in NVD database

Technical Details for CVE-2025-66039

Vulnerability Analysis

This vulnerability (CWE-287: Improper Authentication) exists in the FreePBX Endpoint Manager module's authentication handling logic. When the authentication type is set to "webserver," the system fails to properly validate the credentials provided in the Authorization header. Instead of verifying the authenticity of the credentials, the application accepts any arbitrary value in the Authorization header and associates the resulting session with the target user account.

The flaw represents a fundamental breakdown in the authentication mechanism, allowing attackers to impersonate any user, including administrative accounts, without knowing their passwords. This type of authentication bypass is particularly severe in telephony systems where compromised access could lead to call manipulation, eavesdropping, toll fraud, and exposure of sensitive communication metadata.

Root Cause

The root cause of CVE-2025-66039 lies in improper validation of the Authorization header when the "webserver" authentication type is configured. The authentication logic trusts the presence of an Authorization header without verifying its contents against valid credentials. This design flaw means the system incorrectly assumes that any request with an Authorization header is legitimate, completely bypassing the credential verification step.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:

Identifying a FreePBX system with Endpoint Manager configured to use "webserver" authentication
Crafting an HTTP request with an arbitrary Authorization header value
Targeting a specific user account to hijack their session
Gaining full access to the FreePBX administration interface with the victim's privileges

The vulnerability is particularly dangerous because it can be exploited remotely with minimal complexity and no special privileges required.

text

dialparties.agi is GPL:
 
Zac Sprackett (www.sprackett.com)
-Ported to PHP by the freePBX community.
+Ported to PHP by the FreePBX community.
 
******************************************************************************************
CDR (Call Detail Records) Application:

Source: GitHub Commit Changes

Detection Methods for CVE-2025-66039

Indicators of Compromise

Unexpected HTTP requests to FreePBX management interfaces containing malformed or arbitrary Authorization headers
Session creation events without corresponding successful authentication attempts in logs
Administrative actions performed by accounts that were not actively logged in
Unusual access patterns to Endpoint Manager configuration pages from external IP addresses

Detection Strategies

Monitor web server access logs for requests to FreePBX Endpoint Manager endpoints with unusual Authorization header patterns
Implement web application firewall (WAF) rules to detect and block requests with improperly formatted Authorization headers
Enable verbose authentication logging in FreePBX to capture failed and suspicious authentication attempts
Deploy network intrusion detection systems (IDS) with signatures for authentication bypass attempts against PBX systems

Monitoring Recommendations

Configure alerts for multiple session creations from the same source IP targeting different user accounts
Monitor for administrative configuration changes outside of normal business hours or maintenance windows
Implement anomaly detection for FreePBX API endpoints that may be targeted for exploitation
Review Asterisk and FreePBX logs regularly for signs of unauthorized access or configuration tampering

How to Mitigate CVE-2025-66039

Immediate Actions Required

Upgrade FreePBX to version 16.0.44 or later for the 16.x branch
Upgrade FreePBX to version 17.0.23 or later for the 17.x branch
If immediate patching is not possible, change the authentication type from "webserver" to an alternative method
Restrict network access to FreePBX management interfaces using firewall rules

Patch Information

Sangoma has released security patches addressing this vulnerability. The fixes are included in FreePBX versions 16.0.44 and 17.0.23. Organizations should review the GitHub Security Advisory GHSA-9jvh-mv6x-w698 for detailed patch information. Additional context on security fixes can be found in the FreePBX Security Fixes Overview.

Workarounds

Disable "webserver" authentication type in FreePBX Endpoint Manager and use an alternative authentication method
Place FreePBX management interfaces behind a VPN or IP-restricted access control list
Implement reverse proxy authentication with proper credential validation in front of the FreePBX instance
Enable HTTP Basic Authentication at the web server level as an additional layer of protection

bash

# Example: Restrict access to FreePBX admin interface using iptables
# Allow only trusted management network
iptables -A INPUT -p tcp --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP