Free5GC AMF Bypasses UE Security Capabilities on NGAP PathSwitchRequest

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:L

EPSS

• CVE-2026-42081: 0.27% estimated exploitation activity in the next 30 days; percentile 18.82 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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: 3GPP TS 33.501 §6.7.3.1 requires three actions, none of which are implemented: 1. Verification (SHALL): "The AMF shall verify that the UE's 5G security capabilities received from the target gNB/ng-eNB are the…

Published by the source

7 May 2026, 01:53 UTC

Last modified by the source

8 Jun 2026, 23:46 UTC

Source last checked

26 Oct 2026, 15:23 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-77x9-rf64-92gv

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# Patch Next advisory brief: CVE-2026-42081

Advisory: Free5GC AMF Bypasses UE Security Capabilities on NGAP PathSwitchRequest
IDs: CVE-2026-42081, GHSA-77x9-rf64-92gv
Record: https://patchnext.com/advisories/cve-2026-42081 (revision 1, source checked 26 Oct 2026, 15:23 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/free5gc/amf: affected <= 1.4.3

## Suggested inspection (read-only)
- Go github.com/free5gc/amf: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/free5gc/amf.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-77x9-rf64-92gv (GitHub-reviewed advisory GHSA-77x9-rf64-92gv lists affected ranges: Go github.com/free5gc/amf >=0 <=1.4.3)

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