How severe is CVE-2020-5543?

CVE-2020-5543 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-5543 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-5543?

CVE-2020-5543 affects Mitsubishielectric Iu1-1m20-d Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-5543?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2020-5543 published?

CVE-2020-5543 was published on 2020-03-16 and last updated on 2026-06-17.

CVE-2020-5543

CVE-2020-5543 is a critical-severity vulnerability in Mitsubishielectric Iu1-1m20-d Firmware with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-384.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (80th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-384
Affected product: Mitsubishielectric Iu1-1m20-d Firmware
Published: 2020-03-16
Last modified: 2026-06-17

Description

TCP function included in the firmware of Mitsubishi Electric MELQIC IU1 series IU1-1M20-D firmware version 1.0.7 and earlier does not properly manage sessions, which allows remote attackers to stop the network functions or execute malware via a specially crafted packet.

Frequently asked questions

What is CVE-2020-5543?: TCP function included in the firmware of Mitsubishi Electric MELQIC IU1 series IU1-1M20-D firmware version 1.0.7 and earlier does not properly manage sessions, which allows remote attackers to stop the network functions or execute malware via a specially crafted packet.
How severe is CVE-2020-5543?: CVE-2020-5543 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-5543 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-5543?: CVE-2020-5543 affects Mitsubishielectric Iu1-1m20-d Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-5543?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-5543 published?: CVE-2020-5543 was published on 2020-03-16 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:o:mitsubishielectric:iu1-1m20-d_firmware:*:*:*:*:*:*:*:*

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