42/100 CVSS 7.3 🔴 CVE ANALYSISPublished: May 8, 2026

free5GC's NEF nnef-callback route group is unauthenticated; forged callback requests are accepted into the processing path

### Summary free5GC's NEF mounts the `nnef-callback` route group without inbound OAuth2/bearer-token authorization. A forged or arbitrary bearer token (e.g. `Authorization: Bearer not-a-real-token`) is enough to reach the SMF-callback handler -- the callback body is parsed and dispatched into NEF business logic instead of being rejected at the auth...

7.3

CVSS Score

LOW

Threat Level

Priority /100

TBD

Exploited ITW

Monitor

CISA Status

Sources

🔵

HIGH-PRIORITY SECURITY ADVISORY — Priority Score: 42/100

CVSS 7.3 LOW. SENTINEL APEX recommends immediate patch evaluation. Intelligence from 1 confirmed source(s).

📋 Executive Summary

⚡ Analyst Assessment — SENTINEL APEX v4.0

CYBERDUDEBIVASH SENTINEL APEX has confirmed a LOW-tier threat intelligence signal for CVE-2026-44320 affecting go github.com/free5gc/nef. Composite threat score: 42/100. Intelligence corroborated across 1 source(s): github_advisories. CVSS base score: 7.3. Exploitation probability assessed as HIGH based on vulnerability characteristics.

Intelligence sources: github_advisories

⚠️ Business Impact Analysis

⚠️ Authentication bypass — all access controls circumvented

🔗 Attack Chain Analysis

Step-by-step attack chain based on observed TTPs and vulnerability characteristics:

#	Phase	Attacker Action	MITRE
1	Reconnaissance	Attacker identifies exposed github.com/free5gc/nef instances via Shodan, Censys, or targeted scanning	`TA0043`
2	Initial Access	Unauthenticated exploitation — no credentials required. Single HTTP request sufficient	`T1190`
3	Persistence	Backdoor, scheduled task, or new admin account created for persistent access	`T1053`
4	Command & Control	Attacker establishes persistent C2 channel using HTTPS or DNS tunneling	`T1071`
5	Impact / Objectives	Intellectual property theft, espionage, cryptomining, or preparation for future attack stage	`T1657`

⚠ Deep Dive Analysis

This high-severity vulnerability in go github.com/free5gc/nef (CVSS 7.3) represents a significant attack surface. SENTINEL APEX assesses exploitation to be technically feasible with moderate effort. Organizations running github.com/free5gc/nef in internet-facing or privileged positions face immediate risk.

SENTINEL APEX URGENCY: ELEVATED. Score: 42/100 LOW. Patch before exploitation activity begins.

🎯 MITRE ATT&CK Mapping

Category	Mapping
Primary Tactic	Initial Access
Primary Technique	T1190 — Exploit Public-Facing Application
Sub-Technique	T1078 — Valid Accounts
Weakness (CWE)	CWE-306
Intel Type	🔴 CVE ANALYSIS
Source(s)	github_advisories

🔴 CVE Reference

CVE ID	Reference	Score
CVE-2026-44320	NVD →	7.3
CVE-2026-44320	NVD →	7.3

🔍 Detection Rules — Sigma (SIEM)

Deploy to Splunk, Elastic, Microsoft Sentinel, or QRadar. SOC Pro subscribers receive pre-compiled SIEM-native query packs updated with each pipeline run.

Sigma YAMLtitle: CVE-2026-44320 Exploitation Attempt — go github.com/free5gc/nef
id: b3863e5dd0793fd9-135a
status: experimental
description: Detects exploitation of CVE-2026-44320 in go github.com/free5gc/nef. Priority: LOW. Score: 42/100
author: CYBERDUDEBIVASH SENTINEL APEX v4.0 (bivash@cyberdudebivash.com)
date: 2026-05-08
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-44320
    - https://blog.cyberdudebivash.in/
tags:
    - attack.initial_access
    - attack.t1190
    - cve-2026-44320
    - cve-2026-44320
logsource:
    category: webserver
detection:
    keywords:
        - 'CVE-2026-44320'
        - 'CVE-2026-44320'
        - 'cve-2026-44320'
    condition: keywords
falsepositives:
    - Security scanners
level: medium

📡 Detection Rules — YARA (Endpoint)

Deploy to endpoint detection platforms. Enterprise subscribers receive tuned, FP-validated YARA rule packs.

YARArule CVE_2026_44320_Exploitation {
    meta:
        description = "Detects artifacts related to CVE-2026-44320 exploitation in go github.com/free5gc/nef"
        author      = "CYBERDUDEBIVASH SENTINEL APEX v4.0"
        date        = "2026-05-08"
        severity    = "HIGH"
        cvss        = "7.3"
        priority    = "42/100"
        threat_level = "LOW"
        reference   = "https://nvd.nist.gov/vuln/detail/CVE-2026-44320"
    strings:
        $id_str  = "CVE-2026-44320" ascii nocase
        $product = "github_com_free5gc_nef" ascii nocase wide
    condition:
        any of them
}

🛡️ SOC Response Playbook

1IMMEDIATE (0-1hr): Identify all instances of github.com/free5gc/nef in your environment via CMDB/asset inventory
2IMMEDIATE (0-1hr): Apply vendor patch — no maintenance window exception for LOW threats
3IMMEDIATE (1-2hr): If no patch available: implement WAF rules, ACLs, or network-level compensating controls
4SHORT-TERM (2-4hr): Deploy Sigma detection rule to SIEM — validate alert generation in test environment
5SHORT-TERM (4-8hr): Review logs for exploitation indicators (anomalous github.com/free5gc/nef requests, error spikes)
6SHORT-TERM (8-24hr): Hunt for post-exploitation: new admin accounts, scheduled tasks, lateral movement
7MONITOR: Subscribe to go security advisories for patch updates
8ONGOING: Track SENTINEL APEX intelligence feed for follow-on campaigns targeting github.com/free5gc/nef

📎 Intelligence References

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⚡ CYBERDUDEBIVASH SENTINEL APEX v4.0

Intelligence report generated by CYBERDUDEBIVASH SENTINEL APEX v4.0
Report ID: SENTINEL-CVE-2026-44320-2026-05-08 | Priority: 42/100 LOW | Sources: 1
© 2026 CYBERDUDEBIVASH PRIVATE LIMITED
Republication requires written attribution to CYBERDUDEBIVASH SENTINEL APEX

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