CVE-2021-20596 json
NULL Pointer Dereference in MELSEC-F Series FX3U-ENET firmware version 1.14 and prior, FX3U-ENET-L firmware version 1.14 and prior and FX3U…
published 2021-07-22 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-8014
- cvss
- 7.5
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 2.2%
- EPSS 2.2% chance of exploitation in 30 days, percentile 82%
- public exploits
- 0
- none known
Summary
NULL Pointer Dereference in MELSEC-F Series FX3U-ENET firmware version 1.14 and prior, FX3U-ENET-L firmware version 1.14 and prior and FX3U-ENET-P502 firmware version 1.14 and prior allows a remote unauthenticated attacker to cause a DoS condition in communication by sending specially crafted packets. Control by MELSEC-F series PLC is not affected and system reset is required for recovery.
Patch / fix
Vendor advisories
What the vendors themselves say about their products: affected, fixed or not affected, and what to do.
cisa ICSA-21-201-01 updated cvss 7.5
Mitsubishi Electric MELSEC-F Series
-
Mitsubishi Electric FX3U-ENET <= 1.14 Mitsubishi Electric FX3U-ENET-L <= 1.14 Mitsubishi Electric FX3U-ENET-P502 <= 1.14affected: vendor fix, mitigation “Use a firewall or virtual private network (VPN), etc., to prevent unauthorized access when Internet access is required.” 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
2.17% chance of exploitation in the next 30 days, higher than 82% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| NVD | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| NVD | 2.0 | 5.0 | AV:N/AC:L/Au:N/C:N/I:N/A:P |
Affected products
- n/a MELSEC-F Series FX3U-ENET; FX3U-ENET-L; FX3U-ENET-P502
Classification
- Weakness
-
- CWE-476 NULL Pointer Dereference
References
-
mitsubishielectric.com
/en/psirt/vulnerability/pdf/2021-006_en.pdf
patch, vendor-advisory
-
jvn.jp
/vu/JVNVU94348759/index.html
patch, third-party-advisory
-
us-cert.cisa.gov
/ics/advisories/icsa-21-201-01
third-party-advisory
Sources
- CVE List CVE-2021-20596
- NVD CVE-2021-20596
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