EUVD-2026-322218

fkie_cve-2026-42081

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the AMF in Free5GC does not verify the UE Security Capabilities received in NGAP PathSwitchRequest messages against its locally stored values, as mandated by 3GPP TS 33.501 §6.7.3.1. A malicious gNB can overwrite the AMF's stored UE security capabilities with arbitrary values, which are then propagated in PathSwitchRequest Acknowledge messages and subsequent Handover Request messages. This leads to persistent handover denial-of-service for affected UEs. This vulnerability is fixed in 4.2.2.

GHSA-77x9-rf64-92gv — Free5GC AMF Bypasses UE Security Capabilities on NGAP PathSwitchRequest

Affected: Go: github.com/free5gc/amf

### Summary The AMF in Free5GC v4.2.1 does not verify the UE Security Capabilities received in NGAP PathSwitchRequest messages against its locally stored values, as mandated by 3GPP TS 33.501 §6.7.3.1. A malicious gNB can overwrite the AMF's stored UE security capabilities with arbitrary values, which are then propagated in PathSwitchRequest Acknowledge messages and subsequent Handover Request messages. This leads to persistent handover denial-of-service for affected UEs.

### Details **Affected File:** `amf/internal/ngap/handler.go` — `handlePathSwitchRequestMain` function

**Root Cause:**

When the AMF receives a PathSwitchRequest during an Xn-handover, it processes the UESecurityCapabilities IE by directly overwriting the stored values without comparing them to the previously stored capabilities:

```go if uESecurityCapabilities != nil { amfUe.UESecurityCapability.SetEA1_128_5G(uESecurityCapabilities.NRencryptionAlgorithms.Value.Bytes[0] & 0x80) amfUe.UESecurityCapability.SetEA2_128_5G(uESecurityCapabilities.NRencryptionAlgorithms.Value.Bytes[0] & 0x40) amfUe.UESecurityCapability.SetEA3_128_5G(uESecurityCapabilities.NRencryptionAlgorithms.Value.Bytes[0] & 0x20) amfUe.UESecurityCapability.SetIA1_128_5G(uESecurityCapabilities.NRintegrityProtectionAlgorithms.Value.Bytes[0] & 0x80) amfUe.UESecurityCapability.SetIA2_128_5G(uESecurityCapabilities.NRintegrityProtectionAlgorithms.Value.Bytes[0] & 0x40) amfUe.UESecurityCapability.SetIA3_128_5G(uESecurityCap…

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EUVD-2026-322218

fkie_cve-2026-42081

GHSA-77x9-rf64-92gv — Free5GC AMF Bypasses UE Security Capabilities on NGAP PathSwitchRequest