CVE-2021-20864

Improper access control vulnerability in ELECOM routers (WRC-1167GST2 firmware v1.25 and prior, WRC-1167GST2A firmware v1.25 and prior, WRC-1167GST2H firmware v1.25 and prior, WRC-2533GS2-B firmware v1.52 and prior, WRC-2533GS2-W firmware v1.52 and prior, WRC-1750GS firmware v1.03 and prior, WRC-1750GSV firmware v2.11 and prior, WRC-1900GST firmware v1.03 and prior, WRC-2533GST firmware v1.03 and prior, WRC-2533GSTA firmware v1.03 and prior, WRC-2533GST2 firmware v1.25 and prior, WRC-2533GST2SP firmware v1.25 and prior, WRC-2533GST2-G firmware v1.25 and prior, and EDWRC-2533GST2 firmware v1.25 and prior) allows a network-adjacent unauthenticated attacker to bypass access restriction, and to start the telnet service and execute an arbitrary OS command via unspecified vectors.

Published: 2021-11-30 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-20864 is rated Moderate Risk (49/100): CVSS High severity, with low exploitation likelihood (EPSS 0.50%). Review affected assets and schedule remediation.

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-2021-20864

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 2026-06-15 0.24% 0.50% +0.26%
2 2025-03-30 0.61% 0.24% -0.37%
3 2025-03-29 — 0.61% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-20864

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H 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:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
8.3 2.0 HIGH
AV:A/AC:L/Au:N/C:C/I:C/A:C 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:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 6.5 10.0 [email protected]

Weakness enumeration for CVE-2021-20864

Affected software / configurations for CVE-2021-20864

Vendor Product Version Raw CPE
elecom wrc-1167gst2_firmware <= 1.25 cpe:2.3:o:elecom:wrc-1167gst2_firmware:*:*:*:*:*:*:*:*
elecom wrc-1167gst2a_firmware <= 1.25 cpe:2.3:o:elecom:wrc-1167gst2a_firmware:*:*:*:*:*:*:*:*
elecom wrc-1167gst2h_firmware <= 1.25 cpe:2.3:o:elecom:wrc-1167gst2h_firmware:*:*:*:*:*:*:*:*
elecom wrc-2533gs2-b_firmware <= 1.52 cpe:2.3:o:elecom:wrc-2533gs2-b_firmware:*:*:*:*:*:*:*:*
elecom wrc-2533gs2-w_firmware <= 1.52 cpe:2.3:o:elecom:wrc-2533gs2-w_firmware:*:*:*:*:*:*:*:*
elecom wrc-1750gs_firmware <= 1.03 cpe:2.3:o:elecom:wrc-1750gs_firmware:*:*:*:*:*:*:*:*
elecom wrc-1750gsv_firmware <= 2.11 cpe:2.3:o:elecom:wrc-1750gsv_firmware:*:*:*:*:*:*:*:*
elecom wrc-1900gst_firmware <= 1.03 cpe:2.3:o:elecom:wrc-1900gst_firmware:*:*:*:*:*:*:*:*
elecom wrc-2533gst_firmware <= 1.03 cpe:2.3:o:elecom:wrc-2533gst_firmware:*:*:*:*:*:*:*:*
elecom wrc-2533gst2_firmware <= 1.25 cpe:2.3:o:elecom:wrc-2533gst2_firmware:*:*:*:*:*:*:*:*
elecom wrc-2533gsta_firmware <= 1.03 cpe:2.3:o:elecom:wrc-2533gsta_firmware:*:*:*:*:*:*:*:*
elecom wrc-2533gst2sp_firmware <= 1.25 cpe:2.3:o:elecom:wrc-2533gst2sp_firmware:*:*:*:*:*:*:*:*
elecom wrc-2533gst2-g_firmware <= 1.25 cpe:2.3:o:elecom:wrc-2533gst2-g_firmware:*:*:*:*:*:*:*:*
elecom edwrc-2533gst2_firmware <= 1.25 cpe:2.3:o:elecom:edwrc-2533gst2_firmware:*:*:*:*:*:*:*:*

References for CVE-2021-20864

cvelogic Threat Intelligence