CVE-2025-3755VulnerabilityPublished 29 May 2025Updated 27 Aug 2025

CVE-2025-3755: Mitsubishi Electric MELSEC iQ-F Series FX5U-32MT/ES · Improper Validation of Specified Index, Position, or Offset in Input

Affects Mitsubishi Electric MELSEC iQ-F Series FX5U-32MT/ESSource CVE Database V5

Not known to be exploited · CVSS 9.1 Critical.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

9.1Critical

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

EPSS: 0.8% chance of exploitation in 30 days – higher than 58% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: High

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; 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 impacted component (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).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 29 May 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 2026-10-26.

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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC 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 Corporation MELSEC iQ-F Series FX5U-32MT/ES	Affected *	Fixed in–

AI-suggested

Given the absence of an official patch, European organizations should implement immediate compensating controls to mitigate risk. First, network segmentation should be enforced to isolate MELSEC iQ-F Series PLCs from general IT networks and restrict access to trusted management stations only. Deploy strict firewall rules to block unauthorized inbound traffic to the PLCs, especially from untrusted external networks. Intrusion detection and prevention systems (IDS/IPS) should be tuned to detect anomalous packets targeting the MELSOFT protocol or unusual traffic patterns to the PLCs. Employ network-level authentication and VPNs for remote access to ensure only authorized personnel can communicate with these devices. Regularly monitor logs and network traffic for signs of exploitation attempts. Additionally, organizations should prepare incident response plans specific to PLC DoS scenarios, including procedures for safely resetting affected devices to minimize downtime. Engage with Mitsubishi Electric for timely updates and patches, and plan for rapid deployment once available. Finally, consider implementing application-layer gateways or protocol-aware proxies that can validate and sanitize inputs before they reach the PLCs, reducing the risk of malformed packet exploitation.

Description

Improper Validation of Specified Index, Position, or Offset in Input vulnerability in Mitsubishi Electric Corporation MELSEC iQ-F Series CPU modules allows a remote unauthenticated attacker to read information in the product, to cause a Denial-of-Service (DoS) condition in MELSOFT connection, or to stop the operation of the CPU module (causing a DoS condtion on the CPU module), by sending specially crafted packets. The product is needed to reset for recovery.

Impact

For European organizations, especially those operating in industrial sectors such as manufacturing, energy, utilities, and critical infrastructure, this vulnerability poses a significant risk. The MELSEC iQ-F Series PLCs are widely used in automation and control systems across Europe. Exploitation could lead to unauthorized disclosure of operational data, potentially revealing sensitive process information or intellectual property. More critically, the ability to cause DoS conditions on the MELSOFT connection or the CPU module itself can halt industrial processes, leading to operational downtime, safety hazards, and financial losses. In sectors like energy production or water treatment, such disruptions could have cascading effects on public safety and service continuity. The unauthenticated nature of the attack vector means that attackers do not need prior access or credentials, increasing the threat from external adversaries, including cybercriminals and state-sponsored actors. The lack of available patches further exacerbates the risk, as organizations must rely on compensating controls until a fix is released. The necessity to reset the device manually after an attack implies potential prolonged downtime and increased maintenance efforts. Overall, the vulnerability threatens confidentiality and availability, with no impact on integrity, but the operational disruption alone is critical for industrial environments.

CWE-1285Improper Validation of Specified Index, Position, or Offset in Input (opens in a new tab)
Base weakness
The product receives input that is expected to specify an index, position, or offset into an indexable resource such as a buffer or file, but it does not validate or incorrectly validates that the specified index/position/offset has the required properties.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (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 28 Aug 2025, 01:07 UTC

WeaknessesCWE-1285

Technical details

References

Community reviews

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