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GHSA-6rgm-gr97-x3j5

HighCVSS 8.2 / 10
Published May 7, 2026·Last modified May 7, 2026
Affected Components(0)

No affected components available

Description

Summary

PCF Npcf_SMPolicyControl missing authentication middleware allows unauthenticated access to SM policy handlers and disclosure of subscriber SUPI

Details

In NewServer(), the smPolicyGroup route group is created and routes are applied without attaching the router authorization middleware. In contrast, other PCF service groups such as Npcf_PolicyAuthorization do attach RouterAuthorizationCheck before route registration.

Because the middleware is missing, requests to the following endpoints can reach business logic even when no valid OAuth token is provided:

  • POST /npcf-smpolicycontrol/v1/sm-policies
  • GET /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}
  • POST /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/update
  • POST /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/delete

This is visible at runtime because unauthenticated requests return business-level responses such as 400 or 404 instead of being rejected with 401 before handler execution. Under valid lab preconditions (existing UE/session context and related policy data), unauthenticated POST /sm-policies can succeed with 201, and unauthenticated GET /sm-policies/{id} can succeed with 200 and return policy context containing subscriber identifiers including supi.

The root cause is missing router auth enforcement for Npcf_SMPolicyControl. Upstream also fixed this by adding RouterAuthorizationCheck to smPolicyGroup (and uePolicyGroup) in free5gc/pcf PR #63.

PoC

  1. Deploy free5GC with PCF reachable on the SBI network.
  2. Use the PoC against the PCF service without an Authorization header: 
    go run /home/ubuntu/free5gc/tools/npcf-smpolicy-noauth-poc/main.go \
  --pcf-root /home/ubuntu/free5gc/NFs/pcf \
  --pcf-url http://10.100.200.9:8000 \
  --timeout 4s

Observe that unauthenticated requests to Npcf_SMPolicyControl return business responses instead of 401.

Impact

This is an authentication/authorization bypass on a network-accessible SBI service. Any unauthenticated actor able to reach the PCF SBI interface can invoke Npcf_SMPolicyControl handlers directly.

Risk Scores
Base Score
8.2

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
7.5

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.32%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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High severity
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