# CVE-2026-44321: free5GC SMF unauthenticated denial of service in UPI management

Source: https://junglewise.ai/threats/cve-2026-44321-free5gc-smf-unauthenticated-denial-of-service-in-upi-management  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-27. Updated: 2026-06-09  
License: CC BY 4.0 with a link back

CVE-2026-44321 · Severity: high · CVSS 7.5 · Published 2026-05-27

A vulnerability in the Session Management Function (SMF) of the free5GC 5G core network allows an unauthenticated attacker to crash the service. By sending a specially crafted request to a management endpoint that lacks proper security checks, an attacker can force the entire SMF process to terminate. This results in a complete denial of service, preventing the mobile network from establishing or managing user data sessions until the system is manually restarted.

Technologies: [free5GC Smf](https://junglewise.ai/threats/technologies/smf), [github.com/free5gc/smf (Go)](https://junglewise.ai/threats/technologies/github-com-free5gc-smf). Vendors: [free5GC](https://junglewise.ai/threats/vendors/free5gc), [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-44321 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-44321 being exploited in the wild.

**How severe is CVE-2026-44321?** High severity, with a CVSS score of 7.5, published 27 May 2026.

**Which products and versions are affected?** free5GC Smf < 4.2.2, <= 1.4.3; github.com/free5gc/smf (Go) <= 1.4.3, SEMVER:introduced=0, SEMVER:introduced=0,last_affected=1.4.3.

**Is there a fix for CVE-2026-44321?** 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-2026-44321 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-44321?** Check whether you run free5GC Smf or github.com/free5gc/smf (Go) 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 free5GC Session Management Function (SMF) fails to apply OAuth2 authentication/authorization middleware to the 'UPI' management route group (CWE-306, CWE-862). The 'POST /upi/v1/upNodesLinks' handler passes attacker-controlled JSON to 'UpNodesFromConfiguration()', which performs validation using 'logger.InitLog.Fatalf()'. Because 'Fatalf' in Go's standard logger (or equivalent wrappers) typically calls 'os.Exit(1)', a validation failure—such as providing a UE IP pool that overlaps with an existing one—terminates the entire SMF process rather than just the request goroutine. This allows a remote, unauthenticated attacker to cause a persistent denial of service by repeatedly crashing the SMF. A fix is available in the upstream SMF repository.

## Affected products

- free5gc smf <= 1.4.3

## Identifiers

- CVE-2026-44321
- GHSA-44qj-cghf-9p97
- GO-2026-5109

## Timeline

- 2026-03-22: other: Vulnerability validated in lab environment
- 2026-05-07: disclosed: Advisory published to free5gc/free5gc repository
- 2026-05-08: advisory: GitHub Advisory GHSA-44qj-cghf-9p97 published

## References

- [https://api.github.com/users/LinZiyuu](https://api.github.com/users/LinZiyuu)
- [https://github.com/LinZiyuu](https://github.com/LinZiyuu)
- [https://api.github.com/users/LinZiyuu/gists%7B/gist_id%7D](https://api.github.com/users/LinZiyuu/gists%7B/gist_id%7D)
- [https://api.github.com/users/LinZiyuu/repos](https://api.github.com/users/LinZiyuu/repos)
- [https://avatars.githubusercontent.com/u/104151270?v=4](https://avatars.githubusercontent.com/u/104151270?v=4)
- [https://api.github.com/users/LinZiyuu/events%7B/privacy%7D](https://api.github.com/users/LinZiyuu/events%7B/privacy%7D)

## Related threats

- [free5GC SMF missing authentication in UPI management interface](https://junglewise.ai/threats/cve-2026-44329-free5gc-smf-missing-authentication-in-upi-management-interface)
- [free5GC SMF unauthenticated DoS and state mutation in UPI handler](https://junglewise.ai/threats/cve-2026-44328-free5gc-smf-unauthenticated-dos-and-state-mutation-in-upi-handler)