# CVE-2026-30058: free5gc AMF denial of service in HTTPModifySubscription

Source: https://junglewise.ai/threats/cve-2026-30058-free5gc-amf-denial-of-service-in-httpmodifysubscription  
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-2026-30058 · Severity: high · CVSS 7.5 · Published 2026-08-27

free5gc is an open-source 5G core network implementation. The AMF (Access and Mobility Management Function) component contains a denial-of-service vulnerability in its event subscription modification handler that allows remote attackers to crash the service by sending a specially crafted API request with an invalid path parameter.

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

## Quick answers

**Is CVE-2026-30058 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-30058 being exploited in the wild.

**How severe is CVE-2026-30058?** High severity, with a CVSS score of 7.5, published 27 August 2026.

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

**Is there a fix for CVE-2026-30058?** 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-2026-30058 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-30058?** 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 vulnerability is an improper input validation flaw in the ModifyAMFEventSubscriptionProcedure function within the HTTPModifySubscription handler. The code attempts to slice a JSON Patch path string at a fixed position (characters 11 onwards) without first validating that the path is at least 11 characters long. When a PATCH request is sent with a path shorter than 11 characters (e.g., "/a"), the slice operation causes a runtime panic ("slice bounds out of range"), crashing the AMF process. The vulnerability is reachable over the network via the /namf-evts/v1/subscriptions endpoint without requiring authentication. An attacker can repeatedly trigger this crash to cause a denial of service, preventing legitimate 5G network operations.

## Affected products

- free5gc free5gc v4.0.1

## Timeline

- 2026-01-01: disclosed: Issue opened on GitHub
- 2026-08-27: advisory: CVE-2026-30058 published

## References

- [https://github.com/free5gc/free5gc/issues/754](https://github.com/free5gc/free5gc/issues/754)

## 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)