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CVE-2021-20596

24
FAUCET Score

CVE-2021-20596 is a NULL Pointer Dereference vulnerability affecting Mitsubishi Electric MELSEC-F Series FX3U-ENET, FX3U-ENET-L, and FX3U-ENET-P502 firmware versions 1.14 and prior. A remote, unauthenticated attacker can exploit this by sending specially crafted packets, leading to a Denial of Service (DoS) condition in communication that requires a system reset for recovery. Rated as HIGH severity (CVSS 7.5), this vulnerability is easily exploitable over the network with low attack complexity, impacting availability. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
<= 1.14CPE matchmatch criteria
cpe:2.3:o:mitsubishielectric:fx3u-enet-l_firmware:*:*:*:*:*:*:*:*
<= 1.14CPE matchmatch criteria
cpe:2.3:o:mitsubishielectric:fx3u-enet-p502_firmware:*:*:*:*:*:*:*:*
<= 1.14CPE matchmatch criteria
cpe:2.3:o:mitsubishielectric:fx3u-enet_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.17%
Probability of exploitation in next 30 days
EPSS Percentile
80.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0217 is in the 65th percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

jvn.jp / vu/JVNVU94348759/index.html
PatchThird Party Advisory
us-cert.cisa.gov / ics/advisories/icsa-21-201-01
Third Party Advisory
mitsubishielectric.com / en/psirt/vulnerability/pdf/2021-006_en.pdf
PatchVendor Advisory