free5GC AMF missing default case in Content-Type switch in HTTPUEContextTransfer

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

free5GC AMF provides Access & Mobility Management Function (AMF) for free5GC, an an open-source project for 5th generation (5G) mobile core networks. Prior to version 1.4.3, the `HTTPUEContextTransfer` handler in `internal/sbi/api_communication.go` does not include a `default` case in the `Content-Type` switch statement. When a request arrives with an unsupported `Content-Type`, the deserialization step is silently skipped, `err` remains `nil`, and the processor is invoked with a completely uninitialized `UeContextTransferRequest` object. Version 1.4.3 contains a fix.

Source published

21 Apr 2026 23:54:36 UTC

Source modified

22 Apr 2026 13:11:10 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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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: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 5.5 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

free5GC AMF provides Access & Mobility Management Function (AMF) for free5GC, an an open-source project for 5th generation (5G) mobile core networks. Prior to version 1.4.3, the `HTTPUEContextTransfer` handler in `internal/sbi/api_communication.go` does not include a `default` case in the `Content-Type` switch statement. When a request arrives with an unsupported `Content-Type`, the deserialization step is silently skipped, `err` remains `nil`, and the processor is invoked with a completely uninitialized `UeContextTransferRequest` object. Version 1.4.3 contains a fix.

Source published

Apr 21, 2026, 11:54:36 PM (timezone not stated)

Source modified

Apr 22, 2026, 1:11:10 PM (timezone not stated)

Observed here

1 Nov 2026 07:05:39 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 4.0 · 5.5 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

free5GC AMF provides Access & Mobility Management Function (AMF) for free5GC, an an open-source project for 5th generation (5G) mobile core networks. Prior to version 1.4.3, the `HTTPUEContextTransfer` handler in `internal/sbi/api_communication.go` does not include a `default` case in the `Content-Type` switch statement. When a request arrives with an unsupported `Content-Type`, the deserialization step is silently skipped, `err` remains `nil`, and the processor is invoked with a completely uninitialized `UeContextTransferRequest` object. Version 1.4.3 contains a fix.

Source published

22 Apr 2026 00:16:29 UTC

Source modified

26 Oct 2026 22:10:00 UTC

Observed here

27 Oct 2026 10:10:07 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 5.5 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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

## Summary The `HTTPUEContextTransfer` handler in `internal/sbi/api_communication.go` does not include a `default` case in the `Content-Type` switch statement. When a request arrives with an unsupported `Content-Type`, the deserialization step is silently skipped, `err` remains `nil`, and the processor is invoked with a completely uninitialized `UeContextTransferRequest` object. ## Details In `internal/sbi/api_communication.go`, the `HTTPUEContextTransfer` function handles the `Content-Type` header with a switch statement that only covers `application/json` and `multipart/related`: ```go switch str[0] { case applicationjson: err = openapi.Deserialize(ueContextTransferRequest.JsonData, requestBody, contentType) case multipartrelate: err = openapi.Deserialize(&ueContextTransferRequest, requestBody, contentType) // no default case } if err != nil { // skipped entirely when Content-Type is unsupported c.JSON(http.StatusBadRequest, rsp) return } s.Processor().HandleUEContextTransferRequest(c, ueContextTransferRequest) ``` This is inconsistent with the two analogous handlers in the same file, `HTTPCreateUEContext` and `HTTPN1N2MessageTransfer`, which both correctly include a `default` branch: ```go default: err = fmt.Errorf("wrong content type") ``` The fix is simply to add the same `default` case to `HTTPUEContextTransfer`. ## PoC With a free5GC deployment running, send a POST request to the UE context transfer endpoint using any unsupported `Content-Type` (e.g. `text/plain`): ```bash curl -s -X POST "http://<AMF_IP>/namf-comm/v1/ue-contexts/<ueContextId>/transfer" \\ -H "Content-Type: text/plain" \\ -d '{"test":"data"}' \\ -i ``` **Expected (correct) behavior:** `400 Bad Request` from the SBI layer, rejecting the request due to unsupported Content-Type — consistent with `HTTPCreateUEContext`. **Actual (observed) behavior:** The SBI-layer error check is bypassed and the processor is reached with an empty request object, returning: ``` HTTP/1.1 400 Bad Request {"status": 400, "cause": "MANDATORY_IE_MISSING"} ``` The `MANDATORY_IE_MISSING` cause originates from the processor's internal validation, not from the SBI handler — confirming the processor was called with an uninitialized struct. ## Impact The endpoint is an inter-NF SBI API used during AMF-to-AMF UE context handover. It is not directly reachable from external UEs and requires access to the internal 5GC SBI network. The processor's secondary mandatory field validation prevents any unintended state modification, so there is no direct exploitability. However, the SBI handler layer is the intended first line of defense — relying on the processor to compensate for a missing input check increases fragility and violates defense in depth. Any future change to the processor's validation logic could inadvertently expose the system to processing completely empty request objects.

Source published

22 Apr 2026 19:54:54 UTC

Source modified

25 Jun 2026 23:11:44 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:N/UI:N/S:U/C:N/I:L/A:N

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

Publisher rating · MODERATE

free5GC AMF: Missing default case in Content-Type switch in HTTPUEContextTransfer in github.com/free5gc/amf

Source published

25 Jun 2026 22:34:34 UTC

Source modified

25 Jun 2026 23:01:35 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.