CVE-2025-69253: Free5gc Udr Information Disclosure Issue

CVE-2025-69253 Overview

CVE-2025-69253 is an Information Exposure vulnerability affecting the free5GC open-source 5G mobile core network implementation. The vulnerability exists in the User Data Repository (UDR) component, specifically within the NEF (Network Exposure Function) component's Nnef_PfdManagement service. Versions up to and including 1.4.1 are affected by improper error handling that reliably leaks internal parsing error details to remote clients.

When malformed requests are processed, the NEF component returns verbose error messages containing internal parsing details (such as invalid character 'n' after top-level value), which can be leveraged by attackers to fingerprint the service and gather intelligence for subsequent attacks.

Critical Impact

Remote attackers can exploit verbose error messages to fingerprint free5GC deployments and gather internal implementation details, potentially aiding in the development of more targeted attacks against 5G network infrastructure.

Affected Products

• free5GC UDR versions up to and including 1.4.1
• Deployments utilizing the Nnef_PfdManagement service
• free5GC 5G mobile core network implementations

Discovery Timeline

• 2026-02-24 - CVE-2025-69253 published to NVD
• 2026-02-25 - Last updated in NVD database

Technical Details for CVE-2025-69253

Vulnerability Analysis

This vulnerability falls under CWE-209 (Generation of Error Message Containing Sensitive Information). The free5GC UDR component fails to properly sanitize error messages before returning them to API clients. When the NEF component encounters JSON parsing errors or other internal failures, it exposes detailed error information that reveals implementation-specific details about the underlying service.

The information exposure occurs through the Nnef_PfdManagement service API, which is accessible over the network without requiring authentication for triggering the vulnerable error condition. This allows remote attackers to probe the service with malformed requests and collect error responses that disclose internal application behavior.

Root Cause

The root cause is improper error handling in multiple SBI (Service-Based Interface) processor files within the UDR component. Specifically, after sending error responses to clients, the code fails to include return statements, allowing execution to continue past error handling blocks. This results in verbose internal error details being leaked to remote clients rather than being properly sanitized or logged internally only.

Attack Vector

The vulnerability is exploitable over the network by sending crafted requests to the Nnef_PfdManagement service endpoint. An attacker can:

1. Send malformed JSON payloads to the NEF API endpoints
2. Receive detailed parsing error messages revealing internal implementation details
3. Use collected error patterns to fingerprint the free5GC version and configuration
4. Leverage gathered intelligence for service enumeration and subsequent attacks

The following patch demonstrates the fix applied to address the missing return statements:

// Patch in internal/sbi/processor/amf3_gpp_access_registration_document.go
 		problemDetails := util.ProblemDetailsModifyNotAllowed("")
 		c.Set(sbi.IN_PB_DETAILS_CTX_STR, problemDetails.Cause)
 		c.JSON(int(problemDetails.Status), problemDetails)
+		return
 	}

 	PreHandleOnDataChangeNotify(ueId, CurrentResourceUri, patchItem, origValue, newValue)

Source: Git Commit Update

// Patch in internal/sbi/processor/amf_non3_gpp_access_registration_document.go
 		pd := util.ProblemDetailsSystemFailure(err.Error())
 		c.Set(sbi.IN_PB_DETAILS_CTX_STR, pd.Cause)
 		c.JSON(int(pd.Status), pd)
+		return
 	}
 	PreHandleOnDataChangeNotify(ueId, CurrentResourceUri, patchItem, origValue, newValue)
 	c.Status(http.StatusNoContent)

Source: Git Commit Update

Detection Methods for CVE-2025-69253

Indicators of Compromise

• Unusual volume of malformed API requests targeting NEF/Nnef_PfdManagement endpoints
• Multiple requests with invalid JSON payloads from the same source IP
• HTTP responses containing internal parsing error messages such as invalid character patterns
• Reconnaissance-style traffic patterns probing various API endpoints

Detection Strategies

• Monitor API gateway logs for requests returning 4xx/5xx status codes with verbose error bodies
• Implement alerting for unusual error rates on the Nnef_PfdManagement service
• Deploy web application firewalls (WAF) with rules to detect fingerprinting attempts
• Analyze network traffic for patterns consistent with service enumeration

Monitoring Recommendations

• Enable detailed logging on the UDR component to track API request/response patterns
• Implement rate limiting on API endpoints to mitigate enumeration attacks
• Configure SIEM rules to correlate error responses with source IP reputation data
• Monitor for scanning activity targeting 5G core network service ports

How to Mitigate CVE-2025-69253

Immediate Actions Required

• Apply the official patch from GitHub Pull Request #56 immediately
• Review and update all free5GC UDR instances to the patched version
• Audit API access logs for evidence of prior exploitation attempts
• Implement network segmentation to limit exposure of the Nnef_PfdManagement service

Patch Information

The free5GC project has released an official patch addressing this vulnerability. The fix adds missing return statements after error response handling in multiple processor files, preventing execution from continuing past error conditions and leaking internal details.

Patch Details:

• Repository:free5gc/udr
• Pull Request:GitHub Pull Request #56
• Commit:754d23b0

For more information, refer to the GitHub Security Advisory GHSA-cj2h-x8qm-xgwc.

Workarounds

• No direct application-level workaround is available; applying the official patch is strongly recommended
• Deploy a reverse proxy or API gateway in front of the UDR service to filter and sanitize error responses
• Implement network-level access controls to restrict API access to trusted sources only
• Consider deploying intrusion detection systems (IDS) to monitor for exploitation attempts

# Example: Restricting network access to the UDR service using iptables
# Allow only trusted network ranges to access the UDR API port
iptables -A INPUT -p tcp --dport 8000 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8000 -j DROP