CVE-2025-69208: Free5gc UDR Information Disclosure Flaw

CVE-2025-69208 Overview

CVE-2025-69208 is an Information Exposure vulnerability (CWE-209) affecting the free5GC User Data Repository (UDR), an open-source project implementing 5th generation (5G) mobile core network components. The vulnerability exists in the Nnef_PfdManagement service where the NEF component improperly handles errors, reliably leaking internal parsing error messages to remote clients. This information disclosure can aid attackers in fingerprinting server software and understanding internal logic flows.

Critical Impact

Attackers can leverage verbose error messages to fingerprint the free5GC deployment, identify software versions, and map internal processing logic to facilitate more targeted attacks against 5G core network infrastructure.

Affected Products

• free5GC UDR versions prior to 1.4.1
• free5GC deployments using the Nnef_PfdManagement service
• All installations running vulnerable UDR component (cpe:2.3:a:free5gc:udr:*:*:*:*:*:go:*:*)

Discovery Timeline

• 2026-02-23 - CVE-2025-69208 published to NVD
• 2026-02-25 - Last updated in NVD database

Technical Details for CVE-2025-69208

Vulnerability Analysis

This vulnerability stems from improper error handling within the free5GC UDR component, specifically in the Nnef_PfdManagement service processing. When the NEF component encounters parsing errors, such as encountering an invalid character in JSON input, the detailed internal error message is returned directly to the remote client rather than being sanitized or replaced with a generic error response.

The exposure of internal parsing errors like invalid character 'n' after top-level value provides attackers with valuable reconnaissance information. This can reveal the underlying programming language, framework version, parsing library in use, and the expected data formats. In 5G core network deployments, such information is particularly sensitive as it can be leveraged to craft targeted exploits against the mobile infrastructure.

Root Cause

The root cause is a missing return statement after error responses in the SBI processor code. When an error occurs in functions like getApplicationDataIndividualPfdFromDB, the code correctly logs the error, sets the context, and sends the JSON error response to the client. However, without a return statement, execution continues past the error handling block, potentially sending additional responses or exposing internal state information.

Attack Vector

The vulnerability is exploitable remotely over the network without authentication. An attacker can send malformed requests to the Nnef_PfdManagement service endpoints and observe the detailed error responses. By systematically probing with various malformed inputs, an attacker can:

1. Determine the exact software version and framework in use
2. Map the internal API structure and expected data formats
3. Identify potential injection points based on parsing behavior
4. Build a profile of the target system for more sophisticated attacks

// Security patch in internal/sbi/processor/default.go
// fix: add missing return statements after error responses
 		logger.DataRepoLog.Errorf("getApplicationDataIndividualPfdFromDB err: %s", pd.Detail)
 		c.Set(sbi.IN_PB_DETAILS_CTX_STR, pd.Cause)
 		c.JSON(int(pd.Status), pd)
+		return
 	}
 	c.JSON(http.StatusOK, data)
}

Source: GitHub Commit Update

Detection Methods for CVE-2025-69208

Indicators of Compromise

• HTTP responses containing internal parsing error details such as invalid character messages from UDR endpoints
• Log entries showing detailed error messages being returned to external clients via the Nnef_PfdManagement service
• Unusual patterns of malformed requests targeting the NEF/UDR service endpoints

Detection Strategies

• Monitor HTTP response bodies from UDR services for verbose error messages containing internal parsing details
• Implement web application firewall (WAF) rules to detect and alert on responses containing stack traces or internal error formatting
• Review application logs for patterns of repeated malformed requests that may indicate reconnaissance activity

Monitoring Recommendations

• Enable verbose logging on reverse proxies and API gateways fronting free5GC services to capture response payloads
• Configure alerts for abnormal error rates on the Nnef_PfdManagement service endpoints
• Implement network-level monitoring for unusual request patterns targeting 5G core components

How to Mitigate CVE-2025-69208

Immediate Actions Required

• Upgrade free5GC UDR to version 1.4.1 or later which contains the security fix
• Review and audit all exposed UDR/NEF service endpoints for similar information exposure issues
• Implement API gateway or reverse proxy filtering to sanitize error responses before they reach external clients

Patch Information

The vulnerability is fixed in free5GC UDR version 1.4.1. The patch adds missing return statements after error responses in the SBI processor, preventing execution from continuing after an error has been sent to the client. The fix is available in commit 91bb34bd96e1c89b3fddca80db8b90049da61ebb.

For detailed patch information, refer to the GitHub Security Advisory, GitHub Pull Request, and the GitHub Issue Discussion.

Workarounds

• Deploy an API gateway or reverse proxy that sanitizes error responses before returning them to clients
• Implement network segmentation to restrict access to the Nnef_PfdManagement service from untrusted networks
• Configure custom error pages at the load balancer level to replace detailed error messages with generic responses

# Example: nginx reverse proxy configuration to sanitize error responses
# Add to server block fronting free5GC services

location /nnef-pfdmanagement/ {
    proxy_pass http://udr-service:8000;
    proxy_intercept_errors on;
    error_page 400 401 403 404 500 502 503 504 /custom_error.json;
}

location = /custom_error.json {
    internal;
    default_type application/json;
    return 200 '{"error": "Request could not be processed"}';
}