# CVE-2026-30050: free5gc ModifyAMFEventSubscriptionProcedure denial of service via negative array index

Source: https://junglewise.ai/threats/cve-2026-30050-free5gc-modifyamfeventsubscriptionprocedure-denial-of-service-via  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-27. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-30050 · Severity: high · CVSS 7.5 · Published 2026-08-27

free5gc is an open-source 5G mobile network core implementation. The AMF (Access and Mobility Management Function) handles subscription management for event notifications. A vulnerability in the subscription modification handler allows an attacker to crash the AMF service by submitting a PATCH request with a negative array index, causing a runtime panic and service unavailability.

Technologies: [free5GC](https://junglewise.ai/threats/technologies/free5gc). Vendors: [free5GC](https://junglewise.ai/threats/vendors/free5gc).

## Quick answers

**Is CVE-2026-30050 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-30050 being exploited in the wild.

**How severe is CVE-2026-30050?** High severity, with a CVSS score of 7.5, published 27 August 2026.

**Which products and versions are affected?** free5GC v4.0.1, v4.1.0.

**Is there a fix for CVE-2026-30050?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-30050 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-30050?** Check whether you run free5GC at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The ModifyAMFEventSubscriptionProcedure function in processor/event_exposure.go parses an array index from a JSON Patch request path field using strconv.Atoi() without validating that the parsed integer is non-negative. When a negative index is supplied (e.g., "/eventList/-1"), Go's runtime panics with a "slice bounds out of range" error during slice indexing. The vulnerability is triggered by an unauthenticated PATCH request to the /namf-evts/v1/subscriptions/{id} endpoint. An attacker can cause a denial of service by repeatedly sending crafted requests with negative indices, crashing the AMF process. The fix requires validation of the parsed index before use as a slice accessor.

## Affected products

- free5gc free5gc v4.0.1, v4.1.0

## Timeline

- 2026-01-06: disclosed: Issue reported on GitHub
- 2026-08-27: advisory: CVE-2026-30050 published

## References

- [https://github.com/free5gc/free5gc/issues/776](https://github.com/free5gc/free5gc/issues/776)

## Related threats

- [Free5GC SMF resource exhaustion in PFCP session establishment](https://junglewise.ai/threats/cve-2026-106805-a-resource-exhaustion-issue-exists-in-free5gc-v4-2-3-during-pfcp)
- [Free5GC race condition in GMM handler RanUe context access](https://junglewise.ai/threats/cve-2026-94043-a-vulnerability-was-determined-in-free5gc-up-to-4-2-3-this)
- [Free5GC UPF nil pointer dereference in PFCP Session Report](https://junglewise.ai/threats/cve-2026-75439-free5gc-upf-nil-pointer-dereference-in-pfcp-session-report)
- [free5GC NRF input validation bypass in NF profile registration](https://junglewise.ai/threats/cve-2026-55068-free5gc-nrf-input-validation-bypass-in-nf-profile-registration)
- [free5gc NSSF nil pointer dereference in NssaiAvailabilitySubscriptionCreate](https://junglewise.ai/threats/cve-2026-30073-free5gc-nssf-nil-pointer-dereference-in)