CVE-2026-55068: free5GC NRF nnrf-nfm lacks NF Profile input validation — enables NF Registration Poisoning with arbitrary service endpoints

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 0.6%, percentile 47: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 47% 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/free5gc (Go) < 4.2.2, fixed in 4.2.2. Check your lockfile, including transitive dependencies.

What it is

free5GC is an open-source implementation of the 5G core network. In 4.2.2 and earlier, the NRF RegisterNFInstance handler at PUT /nnrf-nfm/v1/nf-instances/{nfInstanceID} accepts NF Profiles without enforcing UUID format, nfStatus enum values, heartBeatTimer ranges, mandatory profile fields, or nfServices.ipEndPoints address constraints. The invalid profiles are persisted in the MongoDB NfProfile collection and returned by NFDiscover, allowing an attacker with SBI access to advertise attacker-controlled network-function endpoints and redirect control-plane signaling. This can expose credentials and signaling, alter service discovery integrity, and deny service across network functions that trust the NRF. This issue is fixed in version 4.2.3.

From the GitHub advisory

Summary

free5GC NRF (Docker image free5gc-fuzz:latest) accepts NF registration requests without validating any field constraints against 3GPP TS 29.510, allowing unauthenticated attackers to inject fake NF profiles with arbitrary service endpoint IP addresses. All 17 constraint violations tested (UUID format, enum values, numeric ranges, mandatory fields, IP endpoint integrity) were accepted with HTTP 200/201. Legitimate NFs discover these fake profiles via NFDiscover and route control-plane traffic to attacker-controlled endpoints, an attacker with SBI network access can intercept control-plane signaling, harvest OAuth2 credentials, and deny service to subscribers.

---

Details

free5GC NRF's RegisterNFInstance handler (PUT /nnrf-nfm/v1/nf-instances/{nfInstanceID}) accepts the full NF profile body without field-level validation. The following 3GPP TS 29.510 constraints are violated:

Weakness type: CWE-20.

Product: github.com/free5gc/free5gc (Go) · Assigned by: GitHub_M · Published: 2026-08-28

Affected and fixed versions

Severity scores

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

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 no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.59% probability of exploitation activity in the next 30 days; percentile 47.

Timeline

• 2026-08-28 — CVE record published by GitHub_M
• 2026-08-28 — GitHub-reviewed advisory GHSA-x8mj-6p3q-g5pp published (critical)
• 2026-08-31 — CVE record last updated

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-x8mj-6p3q-g5pp github.com
2. CVE.org record CVE-2026-55068 cve.org
3. NVD entry CVE-2026-55068 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
4. github.com github.com
5. github.com github.com
6. github.com github.com
7. github.com github.com

Critical Go advisories · Today’s Security Digest