VulnerabilityPublished 3 Mar 2026Updated 4 Mar 2026

CVE-2026-1876: Mitsubishi Electric MELSEC iQ-F Series FX5-ENET/IP Ethernet Module FX5-ENET/IP · Improper Resource Shutdown or Release

Affects Mitsubishi Electric MELSEC iQ-F Series FX5-ENET/IP Ethernet Module FX5-ENET/IPSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score

8.7High

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 41% 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:H/SC:N/SI:N/SA:N

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: High
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: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
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 3 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
Mitsubishi Electric CorporationMELSEC iQ-F Series FX5-ENET/IP Ethernet Module FX5-ENET/IP	Affected =All versions	Fixed in–

AI-suggested

Implement strict network segmentation to isolate MELSEC iQ-F Series FX5-ENET/IP modules from untrusted networks, limiting exposure to potential attackers.
Deploy firewall rules or access control lists (ACLs) to block or rate-limit unsolicited UDP traffic directed at these devices, especially from external or less trusted internal sources.
Monitor network traffic for unusual spikes in UDP packets targeting the Ethernet modules to detect potential attack attempts early.
Establish incident response procedures to quickly identify and reset affected devices to minimize downtime.
Coordinate with Mitsubishi Electric for updates or patches and apply them promptly once available.
Consider deploying intrusion detection/prevention systems (IDS/IPS) tuned to detect anomalous UDP floods targeting industrial control devices.
Conduct regular security assessments and penetration testing focused on industrial control system networks to identify and remediate exposure points.
Train operational technology (OT) personnel on recognizing and responding to DoS conditions caused by network-based attacks.

Description

Improper Resource Shutdown or Release vulnerability in Mitsubishi Electric Corporation MELSEC iQ-F Series FX5-ENET/IP Ethernet Module FX5-ENET/IP all versions allows a remote attacker to cause a denial-of-service (DoS) condition on the products by continuously sending UDP packets to the products. A system reset of the product is required for recovery.

Impact

The primary impact of CVE-2026-1876 is a denial-of-service condition on the MELSEC iQ-F Series FX5-ENET/IP Ethernet Module, which can disrupt industrial automation processes relying on these devices. This can lead to operational downtime, loss of productivity, and potential safety risks in manufacturing plants, critical infrastructure, and other industrial environments. Since the device requires a system reset to recover, prolonged outages may occur if the attack is sustained or if manual intervention is delayed. The vulnerability affects all versions of the product, increasing the scope of risk. Organizations with large-scale deployments of Mitsubishi Electric automation equipment may face significant operational and financial impacts. Additionally, disruption in critical infrastructure sectors such as energy, transportation, and manufacturing could have broader societal and economic consequences. The lack of authentication and ease of exploitation increase the likelihood of opportunistic attacks, especially in environments with exposed or poorly segmented industrial networks.

CWE-404Improper Resource Shutdown or Release (opens in a new tab)
Class weaknessLikelihood of exploit: Medium
The product does not release or incorrectly releases a resource before it is made available for re-use.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation
It is good practice to be responsible for freeing all resources you allocate and to be consistent with how and where you free memory in a function. If you allocate memory that you intend to free upon completion of the function, you must be sure to free the memory at all exit points for that function including error…
Implementation
Memory should be allocated/freed using matching functions such as malloc/free, new/delete, and new[]/delete[].
Attack patterns
TCP Fragmentation (opens in a new tab)
UDP Fragmentation (opens in a new tab)
ICMP Fragmentation (opens in a new tab)
BlueSmacking (opens in a new tab)
Flooding (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Mar 2026, 17:24 UTC

WeaknessesCWE-404

Technical details

References

Community reviews

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