# CVE-2026-4531: Free5GC AMF handler.go HandleRegistrationComplete denial of service

> Remote attackers can cause a denial of service in Free5GC AMF by exploiting a flaw in the HandleRegistrationComplete function.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Mar 2026
- **Updated:** 23 Mar 2026
- **Also known as:** GHSA-xq44-64rg-8g3h, GO-2026-5767

## What is CVE-2026-4531?

CVE-2026-4531 is a medium-severity denial of service vulnerability in Free5GC, published on 22 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A weakness has been identified in Free5GC 4.1.0. Affected is the function HandleRegistrationComplete of the file internal/gmm/handler.go of the component AMF. Executing a manipulation can lead to denial of service. The attack may be performed from remote. This patch is called 52e9386401ce56ea773c5aa587d4cdf7d53da799. It is best practice to apply a patch to resolve this issue.

Weakness: CWE-404 (Improper Resource Shutdown or Release)

## Which versions are affected by CVE-2026-4531?

3 open source packages ship an affected version, including github.com/free5gc/amf.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/free5gc/amf` | Go | All versions | 1.4.3-0.20260306074636-52e9386401ce |
| `github.com/free5gc/amf` | Go | All versions | 1.4.3-0.20260306074636-52e9386401ce |
| `github.com/free5gc/amf` | Go | All versions | 1.4.3-0.20260306074636-52e9386401ce |

## How do I fix CVE-2026-4531?

Upgrade github.com/free5gc/amf to 1.4.3-0.20260306074636-52e9386401ce or later.

## Is CVE-2026-4531 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4531 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4531 and fix it if it is affected.

What it is: CVE-2026-4531 is a medium-severity denial of service vulnerability in Free5GC, published on 22 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4531 exists.

Affected packages and fixed versions:
- github.com/free5gc/amf (Go): affected all versions; fixed in 1.4.3-0.20260306074636-52e9386401ce
- github.com/free5gc/amf (Go): affected all versions; fixed in 1.4.3-0.20260306074636-52e9386401ce
- github.com/free5gc/amf (Go): affected all versions; fixed in 1.4.3-0.20260306074636-52e9386401ce

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-4531/ (Markdown: https://insights.sbomify.com/CVE-2026-4531/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4531
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4531
- OSV: https://osv.dev/vulnerability/CVE-2026-4531

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4531/
Summaries are generated and may contain mistakes; the official description above is the record.