VulnerabilityPublished 11 Jul 2025

CVE-2025-5241: Mitsubishi Electric MELSEC iQ-F Series FX5U-32MT/ES · Overly Restrictive Account Lockout Mechanism

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

Not known to be exploited · CVSS 5.3 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 38% 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:N/I:N/A:L

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

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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
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 impacted component 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 impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Jul 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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 Corporation MELSEC iQ-F Series FX5U-32MT/ES	Affected *	Fixed in–

AI-suggested

To mitigate this vulnerability, European organizations should implement the following specific measures: 1) Network Segmentation: Isolate MELSEC iQ-F Series PLCs from general IT networks and restrict access to trusted management stations only, using firewalls and VLANs. 2) Access Control: Enforce strict access control policies, including limiting remote access to PLCs via VPNs with multi-factor authentication and IP whitelisting. 3) Monitoring and Alerting: Deploy intrusion detection systems (IDS) and continuous monitoring to detect repeated failed login attempts indicative of lockout attacks. 4) Incident Response Planning: Prepare procedures to quickly reset devices or restore access in case of lockout, minimizing downtime. 5) Vendor Engagement: Maintain communication with Mitsubishi Electric for updates or patches and apply them promptly once available. 6) Physical Security: Ensure physical access to PLCs is restricted to prevent manual resets or tampering. 7) User Training: Educate operators on recognizing lockout symptoms and reporting incidents promptly. These targeted actions go beyond generic advice by focusing on network architecture, access restrictions, and operational readiness tailored to the industrial control environment.

Description

Overly Restrictive Account Lockout Mechanism vulnerability in Mitsubishi Electric Corporation MELSEC iQ-F Series allows a remote unauthenticated attacker to lockout legitimate users for a certain period by repeatedly attempting to login with incorrect passwords. The legitimate users will be unable to login until a certain period has passed after the lockout or until the product is reset.

Impact

For European organizations, especially those operating in industrial sectors such as manufacturing, energy, water treatment, and transportation, this vulnerability poses a risk of operational disruption. The MELSEC iQ-F Series PLCs are commonly deployed in automated control systems across Europe. An attacker exploiting this vulnerability could remotely lock out legitimate operators from accessing critical control devices, leading to downtime or delayed response to process anomalies. While the vulnerability does not allow data theft or manipulation, the denial of service effect could impact production lines, safety systems, or infrastructure management. In regulated industries, such disruptions could also lead to compliance violations or financial penalties. The risk is heightened in environments where remote access to PLCs is enabled without adequate network segmentation or monitoring. Given the lack of patches, organizations must rely on compensating controls to mitigate the threat. The absence of known exploits reduces immediate risk but does not eliminate the potential for future attacks, especially as threat actors often target industrial control systems in Europe due to their critical role in the economy and infrastructure.

CWE-645Overly Restrictive Account Lockout Mechanism (opens in a new tab)
Base weaknessLikelihood of exploit: High
The product contains an account lockout protection mechanism, but the mechanism is too restrictive and can be triggered too easily, which allows attackers to deny service to legitimate users by causing their accounts to be locked out.
Architecture and Design
Implement more intelligent password throttling mechanisms such as those which take IP address into account, in addition to the login name.
Architecture and Design
Implement a lockout timeout that grows as the number of incorrect login attempts goes up, eventually resulting in a complete lockout.
Architecture and Design
Consider alternatives to account lockout that would still be effective against password brute force attacks, such as presenting the user machine with a puzzle to solve (makes it do some computation).
OWASP ASVS 4.0.3
V2.8.5 (opens in a new tab)
V2.8.4 (opens in a new tab)
V9.2.3 (opens in a new tab)
Attack patterns
Inducing Account Lockout (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 11 Jul 2025, 00:46 UTC

WeaknessesCWE-645

Technical details

References

Community reviews

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