Executive Summary

CVE-2026-1682 is a vulnerability in the free5GC SMF component, specifically in the PFCP UDP Endpoint handler function HandlePfcpAssociationReleaseRequest. The issue occurs because the function dereferences a pointer (NodeID) without checking if it is null. If a PFCP Association Release Request message is sent without the mandatory NodeID Information Element, this causes a null pointer dereference, leading to a runtime panic and crashing the SMF process. This vulnerability can be exploited remotely without authentication by sending a crafted PFCP message missing the NodeID, resulting in a denial of service. [1, 2, 3]

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Impact Analysis

This vulnerability can cause a remote denial of service (DoS) on the free5GC SMF component. An attacker can send a specially crafted PFCP Association Release Request missing the mandatory NodeID field, causing the SMF process to crash due to a nil pointer dereference. This crash disrupts the availability of the system, potentially causing service outages or interruptions in the 5G core network functions managed by the SMF. [1, 2, 3]

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Detection Guidance

This vulnerability can be detected by monitoring for crashes or denial of service symptoms in the free5GC SMF process, especially after receiving PFCP Association Release Request messages. Specifically, look for crash logs indicating a nil pointer dereference at handler.go:57 in the function HandlePfcpAssociationReleaseRequest. Additionally, network traffic analysis can be performed to detect PFCP Association Release Request messages that omit the mandatory NodeID Information Element (IE). A proof-of-concept Go program exists that sends such crafted PFCP messages to trigger the crash, which can be adapted for testing. Commands to detect the issue include capturing PFCP UDP traffic on the SMF PFCP port (typically UDP port 8805) using tools like tcpdump or tshark, filtering for PFCP Association Release Requests missing the NodeID IE. For example: 1. Capture PFCP traffic: `sudo tcpdump -i <interface> udp port 8805 -w pfcp_traffic.pcap` 2. Analyze captured traffic for Association Release Requests without NodeID IE using Wireshark or tshark. 3. Monitor SMF logs for runtime panics or crashes referencing handler.go:57. 4. Optionally, use or adapt the publicly available PoC Go program to send crafted PFCP Association Release Requests without NodeID IE to test if the SMF crashes. [2, 3]

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Compliance Impact

The provided resources do not contain information about how CVE-2026-1682 affects compliance with common standards and regulations such as GDPR or HIPAA.

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Mitigation Strategies

The immediate mitigation step is to apply the patch provided by the free5GC project that fixes the nil pointer dereference issue in the PFCP UDP Endpoint handler. This patch adds nil checks for mandatory Information Elements such as NodeID in the HandlePfcpAssociationReleaseRequest function and other related handlers, preventing crashes caused by missing fields. Additionally, the patch improves error handling by sending appropriate PFCP error responses instead of crashing. Until the patch is applied, it is recommended to monitor and filter incoming PFCP Association Release Request messages to block or drop those missing the mandatory NodeID IE to prevent exploitation. Implementing network-level protections such as firewall rules to restrict PFCP traffic to trusted sources can also reduce risk. Ultimately, upgrading free5GC SMF to a version including the patch (post version 4.1.0) is necessary to fully remediate the vulnerability. [1, 4]

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