CVE-2026-44321 free5GC's SMF UPI POST /upi/v1/upNodesLinks exits the SMF process on overlapping UE pools (unauthenticated, reachable Fatalf)
Unauthenticated attackers can crash the free5GC SMF process by sending a specific POST request with overlapping UE pools, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44321?
CVE-2026-44321 is a high-severity denial of service vulnerability in Free5gc Free5gc, published on 27 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's SMF mounts the UPI management route group without inbound OAuth2 middleware. The POST /upi/v1/upNodesLinks create-or-update handler accepts attacker-controlled JSON and passes it directly into UpNodesFromConfiguration(), which calls logger.InitLog.Fatalf(...) on several validation failures. One confirmed path is the UE-IP-pool overlap check: a single unauthenticated POST that adds a new UPF whose pool overlaps an existing UPF terminates the entire SMF process (docker ps shows Exited (1)), not just the goroutine. This vulnerability is fixed in 4.2.2.
Which versions are affected by CVE-2026-44321?
3 open source packages ship an affected version, including github.com/free5gc/smf. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/free5gc/smf Go | All versions | None |
github.com/free5gc/smf Go | All versions to 1.4.3 | None |
github.com/free5gc/smf Go | All versions to 1.4.3 | None |
Products include Free5gc Free5gc.
How do I fix CVE-2026-44321?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-44321 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44321 exists.
Other vulnerabilities in Free5gc Free5gc
- CVE-2026-44327 free5GC: NEF nnef-oam route group is unauthenticated; no-token requests reach the OAM handler
- CVE-2026-44329 free5GC's SMF UPI management interface lacks auth middleware; unauthenticated topology read/write requests reach handlers
- CVE-2026-44330 free5GC's NEF nnef-pfdmanagement API is unauthenticated; forged bearer tokens can read PFD data and create/delete PFD subscriptions
- CVE-2025-63679 Memory corruption in n/a
- CVE-2026-44315 free5GC's NEF 3gpp-pfd-management API is unauthenticated; forged bearer tokens can create, read, and delete PFD transactions
Sources
Also known as GHSA-44qj-cghf-9p97, GO-2026-5109.