CVE-2021-20826

Unprotected transport of credentials vulnerability in IDEC PLCs (FC6A Series MICROSmart All-in-One CPU module v2.32 and earlier, FC6A Series MICROSmart Plus CPU module v1.91 and earlier, WindLDR v8.19.1 and earlier, WindEDIT Lite v1.3.1 and earlier, and Data File Manager v2.12.1 and earlier) allows an attacker to obtain the PLC Web server user credentials from the communication between the PLC and the software. As a result, the complete access privileges to the PLC Web server may be obtained, and manipulation of the PLC output and/or suspension of the PLC may be conducted.

Published: 2021-12-24 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-20826 is rated Low Risk (38.3/100): CVSS High severity, with low exploitation likelihood (EPSS 0.09%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-20826

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-03-30 0.17% 0.09% -0.07%
2 2025-03-29 0.06% 0.17% +0.11%
3 2023-03-07 — 0.06% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-20826

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.6 3.1 HIGH
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L Click to expand
Attack vector (AV:A)
Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.8 4.7 [email protected]
3.3 2.0 LOW
AV:A/AC:L/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:A)
Requires access to an adjacent network segment.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 6.5 2.9 [email protected]

Weakness enumeration for CVE-2021-20826

Affected software / configurations for CVE-2021-20826

Vendor Product Version Raw CPE
idec microsmart_fc6a_firmware <= 2.32 cpe:2.3:o:idec:microsmart_fc6a_firmware:*:*:*:*:*:*:*:*
idec microsmart_plus_fc6a_firmware <= 1.91 cpe:2.3:o:idec:microsmart_plus_fc6a_firmware:*:*:*:*:*:*:*:*
idec data_file_manager <= 2.12.1 cpe:2.3:a:idec:data_file_manager:*:*:*:*:*:*:*:*
idec windedit <= 1.3.1 cpe:2.3:a:idec:windedit:*:*:*:*:*:*:*:*
idec windldr <= 8.19.1 cpe:2.3:a:idec:windldr:*:*:*:*:*:*:*:*

References for CVE-2021-20826

cvelogic Threat Intelligence