CVE-2026-44328

free5GC's SMF UPI DELETE /upi/v1/upNodesLinks/{ref} panics on AN-node deletion via nil UPF dereference; unauthenticated, state-mutating

Three compounding defects on the same SMF SBI surface:

1. Missing inbound authentication (CWE-306) and authorization (CWE-862) on the UPI route group, so the trigger is reachable to any off-path network attacker who can reach SMF on the SBI -- no token, no session, no UE state needed. The same-instance nsmf-oam returning 401 proves the middleware is wired in elsewhere and only missing on UPI.
2. NULL pointer dereference (CWE-476) in DeleteUpNodeLink: the Type == UPNODE_UPF guard only covers the async release call, then upNode.UPF.CancelAssociation() runs unconditionally on AN-typed nodes that have a nil UPF field by construction.
3. Order of operations (CWE-755 / CWE-754): UpNodeDelete(upNodeRef) mutates the in-memory user-plane topology BEFORE the dereference panics, so the topology change lands even though the request returns 500. This makes the bug state-mutating, not just a plain panic.

Any party that can reach SMF on the SBI can:

• Delete arbitrary named entries (e.g. gNB1) from SMF's in-memory user-plane topology anonymously via a single DELETE /upi/v1/upNodesLinks/{ref} request, denying SMF's ability to consider that AN/UPF in subsequent UPF selection / PFCP path establishment for legitimate UE sessions.
• Trigger a panic on the SMF goroutine for the deleted-AN case, even though Gin recovers the goroutine, leaving the topology in the mutated state above.
• Repeat the trigger by name against any AN entry, sustaining the topology denial without ever authenticating.

This is a strict superset of the impact in free5gc/free5gc#887 for this specific code path: same auth bypass, plus a concrete request-triggerable nil deref, plus state mutation that survives the panic.

Affected: free5gc v4.2.1.

Upstream issue: https://github.com/free5gc/free5gc/issues/905
Upstream fix: https://github.com/free5gc/smf/pull/199

A critical operation is accessible without requiring any authentication. Typical impact: any user can invoke the privileged function.

CVE-2026-44328 has a CVSS score of 8.2 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.4.3); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-44328? CVE-2026-44328 is a high-severity missing authentication for critical function vulnerability in github.com/free5gc/smf (go), affecting versions < 1.4.3. It is fixed in 1.4.3. A critical operation is accessible without requiring any authentication.
2. How severe is CVE-2026-44328? CVE-2026-44328 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/free5gc/smf are affected by CVE-2026-44328? github.com/free5gc/smf (go) versions < 1.4.3 is affected.
4. Is there a fix for CVE-2026-44328? Yes. CVE-2026-44328 is fixed in 1.4.3. Upgrade to this version or later.
5. Is CVE-2026-44328 exploitable, and should I be worried? Whether CVE-2026-44328 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44328 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44328? Upgrade github.com/free5gc/smf to 1.4.3 or later.