CVE-2026-4531Public exploitNetwork attack vector

AMF crash via unchecked Registration Complete timer

Published Mar 22, 2026 · Updated Mar 22, 2026

Denial of service in the free5GC 4.1.0 AMF allows remote attackers to crash the AMF with an out-of-sequence NAS message. HandleRegistrationComplete calls StopT3550 without first checking whether the T3550 timer exists, causing a nil dereference for an unexpected Registration Complete. Reachability requires access to the N2 NGAP interface and the crafted registration sequence; a successful trigger terminates the AMF process.

CVSS severity6.9
Medium
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the free5GC 4.1.0 AMF allows remote attackers to crash the AMF with an out-of-sequence NAS message. HandleRegistrationComplete calls StopT3550 without first checking whether the T3550 timer exists, causing a nil dereference for an unexpected Registration Complete. Reachability requires access to the N2 NGAP interface and the crafted registration sequence; a successful trigger terminates the AMF process.

The record

CVE
CVE-2026-4531
Published
Mar 22, 2026
Updated
Mar 22, 2026
Vendor
free5GC
Product
free5GC
Classifications
CWE-404, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

free5GC · free5GCversion=4.1.0

Published CVSS scores

6.9VulDBCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
5.3VulDBCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0VulDBAV:N/AC:L/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-404Improper Resource Shutdown or Release
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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