VulnerabilityPublished 22 Mar 2026Updated 23 Mar 2026

CVE-2026-4531: Free5GC · Denial of Service

Affects Free5GCSource CVE Database V5

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Not known to be exploited · CVSS 6.9 Medium.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score

6.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 37% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Free5GC	Affected =4.1.0	Fixed in–
GitHubfree5gc/free5gc`pkg:github/free5gc/free5gc`Other threats	Affected =4.1.0	Fixed in–

CPE configurations (1)

cpe:2.3:a:free5gc:free5gc:*:*:*:*:*:*:*:*

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AI-suggested

To mitigate CVE-2026-4531, organizations should immediately apply the official patch released by the Free5GC project, identified by commit 52e9386401ce56ea773c5aa587d4cdf7d53da799, which fixes the vulnerability in the HandleRegistrationComplete function. Beyond patching, network operators should implement strict network segmentation and access controls to limit exposure of the AMF to untrusted networks. Deploying anomaly detection and rate limiting on registration completion messages can help detect and mitigate potential exploitation attempts. Regularly monitoring Free5GC logs and system health metrics for signs of crashes or abnormal behavior is recommended. Additionally, organizations should maintain up-to-date backups and have incident response plans tailored for 5G core network components to quickly recover from potential DoS incidents. Finally, consider deploying Free5GC in high-availability configurations to minimize service disruption in case of component failure.

Description

CVE-2026-4531 is a medium-severity denial of service (DoS) vulnerability affecting Free5GC version 4.1.0, specifically in the AMF component's HandleRegistrationComplete function. The flaw allows an unauthenticated remote attacker to cause a DoS condition by manipulating the registration completion process. Exploitation does not require user interaction or privileges, and the attack surface is network-exposed. Although no known exploits are currently reported in the wild, the vulnerability could disrupt 5G core network availability. Applying the vendor patch identified by commit 52e9386401ce56ea773c5aa587d4cdf7d53da799 is recommended to mitigate this issue. Organizations deploying Free5GC 4.1.0 should prioritize patching to maintain service continuity and prevent potential network outages.

Impact

The primary impact of CVE-2026-4531 is denial of service against the AMF component of Free5GC 4.1.0, which can lead to unavailability of 5G core network services. This disruption can prevent legitimate user equipment from completing registration, thereby blocking access to 5G network services including voice, data, and signaling. For organizations relying on Free5GC for 5G core infrastructure—such as telecom operators, research institutions, and private 5G network deployments—this could result in significant service outages and degraded user experience. The lack of authentication and remote exploitability increases the risk of automated attacks or large-scale exploitation attempts. While no known exploits exist currently, the vulnerability could be leveraged by threat actors to cause network instability or as part of a broader attack campaign targeting 5G infrastructure. This could have cascading effects on critical communications, IoT services, and enterprise connectivity dependent on 5G networks.

Summary

CVE-2026-4531 is a vulnerability discovered in Free5GC version 4.1.0, an open-source 5G core network implementation widely used for research, development, and some production environments. The vulnerability resides in the Access and Mobility Management Function (AMF) component, specifically within the HandleRegistrationComplete function located in the internal/gmm/handler.go source file. This function processes the registration completion messages from user equipment (UE). Due to improper handling of certain inputs or state conditions, an attacker can remotely manipulate the registration completion process to trigger a denial of service, causing the AMF to crash or become unresponsive. The vulnerability requires no authentication, no user interaction, and can be exploited over the network, making it relatively easy to exploit. The CVSS 4.0 base score is 6.9, reflecting a medium severity level primarily due to the impact on availability and the ease of exploitation. The vulnerability does not impact confidentiality or integrity. The vendor has released a patch identified by commit 52e9386401ce56ea773c5aa587d4cdf7d53da799 to address this issue. No public exploits or active exploitation have been reported to date. Given the critical role of the AMF in 5G core networks for managing UE registration and mobility, this vulnerability could disrupt network availability and degrade service quality if exploited.

References

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