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VulnerabilityPublished Updated

CVE-2025-8531: Mitsubishi Electric MELSEC-Q Series Q03UDVCPU · Improper Handling of Length Parameter Inconsistency

Affects Mitsubishi Electric MELSEC-Q Series Q03UDVCPUSource CVE Database V5

0

Not known to be exploited · CVSS 6.8 Medium.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score
6.8Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
1.0% chance of exploitation in 30 days – higher than 63% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 Sep 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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.

What to do

AI-suggested

European organizations should first identify if they operate affected Mitsubishi MELSEC-Q Series PLCs with serial numbers in the specified range. Since no patches are currently available, immediate mitigations include: 1) Disabling the user authentication function if it is not required, as the vulnerability is exploitable only when this feature is enabled. 2) Implement strict network segmentation and firewall rules to restrict access to PLC Ethernet interfaces, allowing only trusted management stations and blocking unsolicited external traffic. 3) Deploy intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection tailored to Mitsubishi PLC protocols to detect and block malformed packets. 4) Monitor network traffic for unusual packet patterns indicative of exploitation attempts. 5) Coordinate with Mitsubishi Electric for timely patch releases and apply updates as soon as they become available. 6) Review and harden GX Works2 configurations to ensure compliance without unnecessarily enabling vulnerable features. 7) Conduct regular security assessments and penetration testing focused on ICS environments to identify and remediate exposure.

Description

Improper Handling of Length Parameter Inconsistency vulnerability in Mitsubishi Electric Corporation MELSEC-Q Series Q03UDVCPU, Q04UDVCPU, Q06UDVCPU, Q13UDVCPU, Q26UDVCPU, Q04UDPVCPU, Q06UDPVCPU, Q13UDPVCPU, and Q26UDPVCPU with the first 5 digits of serial No. "24082" to "27081" allows a remote attacker to cause an integer underflow by sending specially crafted packets to the affected product to stop Ethernet communication and the execution of control programs on the product, when the user authentication function is enabled. The user authentication function is enabled by default only when settings are configured by GX Works2, which complies with the Cybersecurity Law of the People's Republic of China, and is normally disabled.

References

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