CVE-2021-20988 | Hilscher rcX RTOS: Wrong handling of the UDP checksum

In Hilscher rcX RTOS versions prios to V2.1.14.1 the actual UDP packet length is not verified against the length indicated by the packet. This may lead to a denial of service of the affected device.

Published: 2021-05-13 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-20988 is rated Moderate Risk (55.3/100): 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-2021-20988

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 0.28% 0.99% +0.71%
2 2025-03-17 0.15% 0.28% +0.13%
3 2024-12-17 — 0.15% —

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-20988

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.6 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
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 4.0 [email protected]
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-2021-20988

Affected software / configurations for CVE-2021-20988

Vendor Product Version Raw CPE
hilscher rcx_rtos < 2.1.14.1 cpe:2.3:a:hilscher:rcx_rtos:*:*:*:*:*:*:*:*
pepperl-fuchs ice1-16di-g60l-v1d_firmware <= f10017 cpe:2.3:o:pepperl-fuchs:ice1-16di-g60l-v1d_firmware:*:*:*:*:*:*:*:*
pepperl-fuchs ice1-16dio-g60l-c1-v1d_firmware <= f10017 cpe:2.3:o:pepperl-fuchs:ice1-16dio-g60l-c1-v1d_firmware:*:*:*:*:*:*:*:*
pepperl-fuchs ice1-16dio-g60l-v1d_firmware <= f10017 cpe:2.3:o:pepperl-fuchs:ice1-16dio-g60l-v1d_firmware:*:*:*:*:*:*:*:*
pepperl-fuchs ice1-8di8do-g60l-c1-v1d_firmware <= f10017 cpe:2.3:o:pepperl-fuchs:ice1-8di8do-g60l-c1-v1d_firmware:*:*:*:*:*:*:*:*
pepperl-fuchs ice1-8di8do-g60l-v1d_firmware <= f10017 cpe:2.3:o:pepperl-fuchs:ice1-8di8do-g60l-v1d_firmware:*:*:*:*:*:*:*:*
pepperl-fuchs ice1-8iol-g30l-v1d_firmware <= f10017 cpe:2.3:o:pepperl-fuchs:ice1-8iol-g30l-v1d_firmware:*:*:*:*:*:*:*:*
pepperl-fuchs ice1-8iol-g60l-v1d_firmware <= f10017 cpe:2.3:o:pepperl-fuchs:ice1-8iol-g60l-v1d_firmware:*:*:*:*:*:*:*:*
pepperl-fuchs ice1-8iol-s2-g60l-v1d_firmware <= f10017 cpe:2.3:o:pepperl-fuchs:ice1-8iol-s2-g60l-v1d_firmware:*:*:*:*:*:*:*:*

References for CVE-2021-20988

cvelogic Threat Intelligence