CVE-2026-42083

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.

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2026-42083 has a CVSS score of 8.2 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.4.3); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-42083? CVE-2026-42083 is a high-severity missing authorization vulnerability in github.com/free5gc/pcf (go), affecting versions < 1.4.3. It is fixed in 1.4.3. The application does not perform an authorization check before performing a sensitive operation.
2. How severe is CVE-2026-42083? CVE-2026-42083 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/free5gc/pcf are affected by CVE-2026-42083? github.com/free5gc/pcf (go) versions < 1.4.3 is affected.
4. Is there a fix for CVE-2026-42083? Yes. CVE-2026-42083 is fixed in 1.4.3. Upgrade to this version or later.
5. Is CVE-2026-42083 exploitable, and should I be worried? Whether CVE-2026-42083 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-42083 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-42083? Upgrade github.com/free5gc/pcf to 1.4.3 or later.