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CVE-2026-42082

free5GC: Missing Concurrent NAS SMC Validation During NGAP Handover

3.7 Low

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the AMF in Free5GC does not enforce the concurrent security procedure rules defined in 3GPP TS 33.501 §6.9.5.1. The AMF does not check for ongoing N2 handover procedures before initiating a NAS Security Mode Command, and vice versa. This can lead to mismatches between NAS and AS security contexts in the network and the UE. This vulnerability is fixed in 4.2.2.

Attack profile

How easy it is to exploit

Attack vector
Adjacent network
Complexity
High
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
Low
Availability
Low

Exploit likelihood

0.25%Up 0.2 points since May 28, 2026
90%50%10%1%

What each source reports

CVE List Score used 3.7

free5GC: Missing Concurrent NAS SMC Validation During NGAP Handover

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the AMF in Free5GC does not enforce the concurrent security procedure rules defined in 3GPP TS 33.501 §6.9.5.1. The AMF does not check for ongoing N2 handover procedures before initiating a NAS Security Mode Command, and vice versa. This can lead to mismatches between NAS and AS security contexts in the network and the UE. This vulnerability is fixed in 4.2.2.

Record
CVE-2026-42082
CVSS 3.1
3.7 LowCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L
Weakness
CWE-358
Updated
2026-11-02
EUVDEUVD-2026-32556 3.7

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the AMF in Free5GC does not enforce the concurrent security procedure rules defined in 3GPP TS 33.501 §6.9.5.1. The AMF does not check for ongoing N2 handover procedures before initiating a NAS Security Mode Command, and vice versa. This can lead to mismatches between NAS and AS security contexts in the network and the UE. This vulnerability is fixed in 4.2.2.

Record
EUVD-2026-32556
CVSS 3.1
3.7 LowCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L
Updated
2026-11-02
GitHub AdvisoriesGHSA-vrrx-58h3-prmh 3.7

Free5GC AMF has Missing Concurrent NAS SMC Validation During NGAP Handover

Summary

The AMF in Free5GC v4.2.1 does not enforce the concurrent security procedure rules defined in 3GPP TS 33.501 §6.9.5.1. The AMF does not check for ongoing N2 handover procedures before initiating a NAS Security Mode Command, and vice versa. This can lead to mismatches between NAS and AS security contexts in the network and the UE.

Details

Vulnerability Type: CWE-358 (Improperly Implemented Security Check for Standard)

Affected File: internal/ngap/handler.go — handleHandoverRequiredMain() and internal/gmm/sm.go — SecurityMode()

Root Cause:

3GPP TS 33.501 §6.9.5.1 states:

"Concurrent runs of security procedures may, in certain situations, lead to mismatches between security contexts in the network and the UE. In order to avoid such mismatches, the following rules shall be adhered to:

  1. AMF shall not initiate any of the N2 procedures including a new key towards a UE if a NAS Security Mode Command procedure is ongoing with the UE.
  2. The AMF shall not initiate a NAS Security Mode Command towards a UE if one of the N2 procedures including a new key is ongoing with the UE."

Free5GC AMF uses an OnGoing state tracking mechanism (SetOnGoing(), GetOnGoing()) with OnGoingProcedureN2Handover type. However, the cross-procedure checks required by §6.9.5.1 are not implemented:

Rule 2 violation: SecurityMode() in internal/gmm/sm.go sends SMC on EntryEvent without checking if N2 handover is ongoing.

Rule 1 violation: handleHandoverRequiredMain() in internal/ngap/handler.go calls SetOnGoing(OnGoingProcedureN2Handover) without checking if SMC is ongoing.

Why NH/NCC and SMC are related:

SMC activates a new KAMF, which changes the basis for NH key derivation. The N2 HandoverRequest includes NH/NCC derived from the old KAMF. If both procedures run concurrently, the target gNB and UE derive different KgNB keys, breaking AS security.

PoC

Source code evidence:

Free5GC AMF internal/gmm/sm.go — SecurityMode():

func SecurityMode(state *fsm.State, event fsm.EventType, args fsm.ArgsType) {
    switch event {
    case fsm.EntryEvent:
        // No check for OnGoing N2 procedure
        // Directly proceeds to SMC

Free5GC AMF internal/ngap/handler.go — handleHandoverRequiredMain():

amfUe.SetOnGoing(sourceUe.Ran.AnType, &context.OnGoing{
    Procedure: context.OnGoingProcedureN2Handover,
})
// No check for ongoing SMC before setting N2

Packet Evidence (pcap available):

| Packet | Time | Message | Description | |--------|------|---------|-------------| | #1 | 0.000s | HandoverRequired | gNB_A requests handover | | #18 | 0.002s | HandoverRequest | N2 started (NH/NCC included) | | | | (no response from gNB_B) | N2 ongoing | | #28 | 2.062s | Registration request | UE re-registers (same SUPI) | | #63 | 2.069s | Authentication request | | | #64 | 2.070s | Authentication response | | | #71 | 2.072s | Security mode command | SMC during N2 ongoing = Rule 2 violation | NGAPHandover-N2-SMC-Concurrent.zip

Impact

Integrity (MEDIUM): Concurrent NAS and AS security procedures can cause security context mismatches between UE, AMF, and gNB. The SMC activates a new KAMF while the N2 HandoverRequest carries NH/NCC derived from the old KAMF, resulting in KgNB derivation mismatch.

Availability (LOW): Security context mismatch may cause handover failure or security verification failures.

Record
GHSA-vrrx-58h3-prmh
CVSS 3.1
3.7 LowCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L
Weakness
CWE-358
Updated
2026-11-02
NVD 3.7

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the AMF in Free5GC does not enforce the concurrent security procedure rules defined in 3GPP TS 33.501 §6.9.5.1. The AMF does not check for ongoing N2 handover procedures before initiating a NAS Security Mode Command, and vice versa. This can lead to mismatches between NAS and AS security contexts in the network and the UE. This vulnerability is fixed in 4.2.2.

Record
CVE-2026-42082
CVSS 3.1
3.7 LowCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L
CVSS 3.1
5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
Weakness
CWE-358
Updated
2026-11-02
OSV 3.7

free5GC: Missing Concurrent NAS SMC Validation During NGAP Handover

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the AMF in Free5GC does not enforce the concurrent security procedure rules defined in 3GPP TS 33.501 §6.9.5.1. The AMF does not check for ongoing N2 handover procedures before initiating a NAS Security Mode Command, and vice versa. This can lead to mismatches between NAS and AS security contexts in the network and the UE. This vulnerability is fixed in 4.2.2.

Record
CVE-2026-42082
CVSS 3.1
3.7 LowCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L
Weakness
CWE-358
Updated
2026-11-02
OSVGHSA-vrrx-58h3-prmh 3.7

Free5GC AMF has Missing Concurrent NAS SMC Validation During NGAP Handover

Summary

The AMF in Free5GC v4.2.1 does not enforce the concurrent security procedure rules defined in 3GPP TS 33.501 §6.9.5.1. The AMF does not check for ongoing N2 handover procedures before initiating a NAS Security Mode Command, and vice versa. This can lead to mismatches between NAS and AS security contexts in the network and the UE.

Details

Vulnerability Type: CWE-358 (Improperly Implemented Security Check for Standard)

Affected File: internal/ngap/handler.go — handleHandoverRequiredMain() and internal/gmm/sm.go — SecurityMode()

Root Cause:

3GPP TS 33.501 §6.9.5.1 states:

"Concurrent runs of security procedures may, in certain situations, lead to mismatches between security contexts in the network and the UE. In order to avoid such mismatches, the following rules shall be adhered to:

  1. AMF shall not initiate any of the N2 procedures including a new key towards a UE if a NAS Security Mode Command procedure is ongoing with the UE.
  2. The AMF shall not initiate a NAS Security Mode Command towards a UE if one of the N2 procedures including a new key is ongoing with the UE."

Free5GC AMF uses an OnGoing state tracking mechanism (SetOnGoing(), GetOnGoing()) with OnGoingProcedureN2Handover type. However, the cross-procedure checks required by §6.9.5.1 are not implemented:

Rule 2 violation: SecurityMode() in internal/gmm/sm.go sends SMC on EntryEvent without checking if N2 handover is ongoing.

Rule 1 violation: handleHandoverRequiredMain() in internal/ngap/handler.go calls SetOnGoing(OnGoingProcedureN2Handover) without checking if SMC is ongoing.

Why NH/NCC and SMC are related:

SMC activates a new KAMF, which changes the basis for NH key derivation. The N2 HandoverRequest includes NH/NCC derived from the old KAMF. If both procedures run concurrently, the target gNB and UE derive different KgNB keys, breaking AS security.

PoC

Source code evidence:

Free5GC AMF internal/gmm/sm.go — SecurityMode():

func SecurityMode(state *fsm.State, event fsm.EventType, args fsm.ArgsType) {
    switch event {
    case fsm.EntryEvent:
        // No check for OnGoing N2 procedure
        // Directly proceeds to SMC

Free5GC AMF internal/ngap/handler.go — handleHandoverRequiredMain():

amfUe.SetOnGoing(sourceUe.Ran.AnType, &context.OnGoing{
    Procedure: context.OnGoingProcedureN2Handover,
})
// No check for ongoing SMC before setting N2

Packet Evidence (pcap available):

| Packet | Time | Message | Description | |--------|------|---------|-------------| | #1 | 0.000s | HandoverRequired | gNB_A requests handover | | #18 | 0.002s | HandoverRequest | N2 started (NH/NCC included) | | | | (no response from gNB_B) | N2 ongoing | | #28 | 2.062s | Registration request | UE re-registers (same SUPI) | | #63 | 2.069s | Authentication request | | | #64 | 2.070s | Authentication response | | | #71 | 2.072s | Security mode command | SMC during N2 ongoing = Rule 2 violation | NGAPHandover-N2-SMC-Concurrent.zip

Impact

Integrity (MEDIUM): Concurrent NAS and AS security procedures can cause security context mismatches between UE, AMF, and gNB. The SMC activates a new KAMF while the N2 HandoverRequest carries NH/NCC derived from the old KAMF, resulting in KgNB derivation mismatch.

Availability (LOW): Security context mismatch may cause handover failure or security verification failures.

Record
GHSA-vrrx-58h3-prmh
CVSS 3.1
3.7 LowCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L
Weakness
CWE-358
Updated
2026-11-02
OSVGO-2026-5673 No score

Free5GC AMF has Missing Concurrent NAS SMC Validation During NGAP Handover in github.com/free5gc/amf

Free5GC AMF has Missing Concurrent NAS SMC Validation During NGAP Handover in github.com/free5gc/amf

Record
GO-2026-5673
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/free5gc/amf
Go
 through 1.4.3 None known
github.com/free5gc/amf
Go
 All versions None known
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-42082 is a low vulnerability (CVSS 3.7) in Free5gc, published May 7, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.25%, the 16th percentile. No source names a fixed version.

References

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