CVE-2026-44326: free5GC's NEF 3gpp-traffic-influence API is unauthenticated; missing or forged bearer tokens can create, read, patch, and delete subscriptions

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.5%, percentile 44: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 44% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes github.com/free5gc/nef (Go) <= 1.2.3, no fixed version listed. Check your lockfile, including transitive dependencies.

What it is

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's NEF mounts the 3gpp-traffic-influence API without inbound OAuth2/bearer-token authorization. A network attacker who can reach NEF on the SBI can create, read, patch, and delete traffic-influence subscriptions either with no Authorization header at all, or with a forged bearer token (e.g. Authorization: Bearer not-a-real-token). This includes creating AnyUeInd=true subscriptions intended to affect group / any-UE traffic steering. The route group is also reachable even when the running config's ServiceList does not declare it, so operators who think they disabled the service via config are still exposed. This vulnerability is fixed in 4.2.2.

From the GitHub advisory

Summary free5GC's NEF mounts the 3gpp-traffic-influence API without inbound OAuth2/bearer-token authorization. A network attacker who can reach NEF on the SBI can create, read, patch, and delete traffic-influence subscriptions either with no Authorization header at all, or with a forged bearer token (e.g. Authorization: Bearer not-a-real-token). This includes creating AnyUeInd=true subscriptions intended to affect group / any-UE traffic steering. The route group is also reachable even when the running config's ServiceList does not declare it, so operators who think they disabled the service via config are still exposed.

This is the highest-impact NEF service exposure observed in the lab because it enables unauthenticated state changes on traffic-steering policy objects rather than read-only exposure.

Details Validated against the NEF container in the official Docker compose lab. - Source repo tag: v4.2.1 - Running Docker image: free5gc/nef:v4.2.0 - Runtime NEF commit: 5ce35eab - Docker validation date: 2026-03-11

NEF advertises OAuth2 setting receive from NRF: true, and its ServiceList only declares nnef-pfdmanagement and nnef-oam. Despite that, the 3gpp-traffic-influence route group is mounted and reachable with no inbound auth middleware.

Code evidence (paths in free5gc/nef): - Route group mounted without auth middleware: NFs/nef/internal/sbi/server.go:48 - CRUD routes exposed at /:afID/subscriptions and /:afID/subscriptions/:subID: NFs/nef/internal/sbi/apiti.go:13 - POST allocates AF/subscription state and writes traffic-influence data: NFs/nef/internal/sbi/processor/ti.go:50 - PATCH looks up and updates the subscription, then calls UDR/PCF: NFs/nef/internal/sbi/processor/ti.go:279 - DELETE looks up and removes the subscription: NFs/nef/internal/sbi/processor/ti.go:355 - NEF context only exposes outbound token acquisition (GetTokenCtx); there is no inbound authorization path: NFs/nef/internal/context/nefcontext.go:153 - Config validation only allows nnef-pfdmanagement and nnef-oam: NFs/nef/pkg/factory/config.go:126

Weakness type: CWE-862.

Product: github.com/free5gc/nef (Go) · Assigned by: GitHub_M · Published: 2026-05-27

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.53% probability of exploitation activity in the next 30 days; percentile 44.

Timeline

• 2026-05-08 — GitHub-reviewed advisory GHSA-3p28-73q7-45xp published (critical)
• 2026-05-27 — CVE record last updated
• 2026-05-27 — CVE record published by GitHub_M

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-3p28-73q7-45xp github.com
2. CVE.org record CVE-2026-44326 cve.org
3. NVD entry CVE-2026-44326 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

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