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Fencer Vulns
critical 9.8

CVE-2020-5653 json

Buffer overflow vulnerability in TCP/IP function included in the firmware of MELSEC iQ-R series (RJ71EIP91 EtherNet/IP Network Interface Mo…

published 2020-10-30 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-26814

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.2%
EPSS 3.2% chance of exploitation in 30 days, percentile 88%
public exploits
0
none known

Summary

Buffer overflow vulnerability in TCP/IP function included in the firmware of MELSEC iQ-R series (RJ71EIP91 EtherNet/IP Network Interface Module First 2 digits of serial number are '02' or before, RJ71PN92 PROFINET IO Controller Module First 2 digits of serial number are '01' or before, RD81DL96 High Speed Data Logger Module First 2 digits of serial number are '08' or before, RD81MES96N MES Interface Module First 2 digits of serial number are '04' or before, and RD81OPC96 OPC UA Server Module First 2 digits of serial number are '04' or before) allows a remote unauthenticated attacker to stop the network functions of the products or execute a malicious program via a specially crafted packet.

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

cisa ICSA-20-303-02 updated cvss 9.8

Mitsubishi Electric MELSEC iQ-R

  • Mitsubishi Electric EtherNet/IP Network Interface Module RJ71EIP91 <= first 2 digits of serial number are 02 Mitsubishi Electric High Speed Data Logger Module RD81DL96 <= first 2 digits of serial number are 08 Mitsubishi Electric MES Interface Module RD81MES96N <= first 2 digits of serial number are 04 Mitsubishi Electric OPC UA Server Module RD81OPC96 <= first 2 digits of serial number are 04 Mitsubishi Electric PROFINET IO Controller Module RJ71PN92 <= first 2 digits of serial number are 01
    affected: mitigation “Block access from untrusted networks and hosts through firewalls.” mitsubishielectric.com

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

Exploit prediction

3.21% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Mitsubishi Electric Corporation MELSEC iQ-R series

Classification

Weakness
  • CWE-120 Buffer Copy without Checking Size of Input

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.