CVE-2021-31340

A vulnerability has been identified in SIMATIC RF166C (All versions > V1.1 and < V1.3.2), SIMATIC RF185C (All versions > V1.1 and < V1.3.2), SIMATIC RF186C (All versions > V1.1 and < V1.3.2), SIMATIC RF186CI (All versions > V1.1 and < V1.3.2), SIMATIC RF188C (All versions > V1.1 and < V1.3.2), SIMATIC RF188CI (All versions > V1.1 and < V1.3.2), SIMATIC RF360R (All versions < V2.0), SIMATIC Reader RF610R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF610R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF610R FCC (All versions > V3.0 < V4.0), SIMATIC Reader RF615R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF615R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF615R FCC (All versions > V3.0 < V4.0), SIMATIC Reader RF650R ARIB (All versions > V3.0 < V4.0), SIMATIC Reader RF650R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF650R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF650R FCC (All versions > V3.0 < V4.0), SIMATIC Reader RF680R ARIB (All versions > V3.0 < V4.0), SIMATIC Reader RF680R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF680R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF680R FCC (All versions > V3.0 < V4.0), SIMATIC Reader RF685R ARIB (All versions > V3.0 < V4.0), SIMATIC Reader RF685R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF685R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF685R FCC (All versions > V3.0 < V4.0). Affected devices do not properly handle large numbers of incoming connections. An attacker may leverage this to cause a Denial-of-Service situation.

Published: 2021-06-08 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-31340 is rated Moderate Risk (50.7/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.99%). 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-2021-31340

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 0.48% 0.99% +0.51%
2 2025-04-20 0.57% 0.48% -0.09%
3 2025-03-30 — 0.57% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-31340

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-31340

Affected software / configurations for CVE-2021-31340

Vendor Product Version Raw CPE
siemens simatic_rf166c_firmware > 1.1, < 1.3.2 cpe:2.3:o:siemens:simatic_rf166c_firmware:*:*:*:*:*:*:*:*
siemens simatic_rf185c_firmware > 1.1, < 1.3.2 cpe:2.3:o:siemens:simatic_rf185c_firmware:*:*:*:*:*:*:*:*
siemens simatic_rf186c_firmware > 1.1, < 1.3.2 cpe:2.3:o:siemens:simatic_rf186c_firmware:*:*:*:*:*:*:*:*
siemens simatic_rf186ci_firmware > 1.1, < 1.3.2 cpe:2.3:o:siemens:simatic_rf186ci_firmware:*:*:*:*:*:*:*:*
siemens simatic_rf188c_firmware > 1.1, < 1.3.2 cpe:2.3:o:siemens:simatic_rf188c_firmware:*:*:*:*:*:*:*:*
siemens simatic_rf188ci_firmware > 1.1, < 1.3.2 cpe:2.3:o:siemens:simatic_rf188ci_firmware:*:*:*:*:*:*:*:*
siemens simatic_rf360r_firmware < 2.0 cpe:2.3:o:siemens:simatic_rf360r_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf610r_cmiit_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf610r_cmiit_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf610r_etsi_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf610r_etsi_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf610r_fcc_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf610r_fcc_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf615r_cmiit_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf615r_cmiit_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf615r_etsi_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf615r_etsi_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf615r_fcc_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf615r_fcc_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf650r_cmiit_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf650r_cmiit_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf650r_etsi_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf650r_etsi_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf650r_fcc_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf650r_fcc_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf650r_arib_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf650r_arib_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf680r_cmiit_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf680r_cmiit_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf680r_etsi_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf680r_etsi_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf680r_fcc_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf680r_fcc_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf680r_arib_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf680r_arib_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf685r_cmiit_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf685r_cmiit_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf685r_etsi_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf685r_etsi_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf685r_fcc_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf685r_fcc_firmware:*:*:*:*:*:*:*:*
siemens simatic_reader_rf685r_arib_firmware >= 3.0, < 4.0 cpe:2.3:o:siemens:simatic_reader_rf685r_arib_firmware:*:*:*:*:*:*:*:*

References for CVE-2021-31340

URL Tags
https://cert-portal.siemens.com/productcert/pdf/ssa-787292.pdf Mitigation Patch Vendor Advisory
cvelogic Threat Intelligence