CVE-2021-34593 | CODESYS V2 runtime: unauthenticated invalid requests may result in denial-of-service

Exp

In CODESYS V2 Runtime Toolkit 32 Bit full and PLCWinNT prior to versions V2.4.7.56 unauthenticated crafted invalid requests may result in several denial-of-service conditions. Running PLC programs may be stopped, memory may be leaked, or further communication clients may be blocked from accessing the PLC.

Published: 2021-10-26 Last update: 2025-08-15 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-34593 is rated High Exploit Risk (72.6/100): CVSS High severity, with medium exploitation likelihood (EPSS 2.65%). 2 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

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

Public exploit references (Exploit-DB) for CVE-2021-34593

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-34593

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 4.30% 2.65% -1.66%
2 2026-04-25 1.59% 4.30% +2.71%
3 2025-11-21 — 1.59% —

Full EPSS history (26 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-34593

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]
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-2021-34593

Affected software / configurations for CVE-2021-34593

Vendor Product Version Raw CPE
wago 750-8202_firmware < fw20 cpe:2.3:o:wago:750-8202_firmware:*:*:*:*:*:*:*:*
wago 750-8203_firmware < fw20 cpe:2.3:o:wago:750-8203_firmware:*:*:*:*:*:*:*:*
wago 750-8204_firmware < fw20 cpe:2.3:o:wago:750-8204_firmware:*:*:*:*:*:*:*:*
wago 750-8206_firmware < fw20 cpe:2.3:o:wago:750-8206_firmware:*:*:*:*:*:*:*:*
wago 750-8207_firmware < fw20 cpe:2.3:o:wago:750-8207_firmware:*:*:*:*:*:*:*:*
wago 750-8208_firmware < fw20 cpe:2.3:o:wago:750-8208_firmware:*:*:*:*:*:*:*:*
wago 750-8210_firmware < fw20 cpe:2.3:o:wago:750-8210_firmware:*:*:*:*:*:*:*:*
wago 750-8211_firmware < fw20 cpe:2.3:o:wago:750-8211_firmware:*:*:*:*:*:*:*:*
wago 750-8212_firmware < fw20 cpe:2.3:o:wago:750-8212_firmware:*:*:*:*:*:*:*:*
wago 750-8213_firmware < fw20 cpe:2.3:o:wago:750-8213_firmware:*:*:*:*:*:*:*:*
wago 750-8214_firmware < fw20 cpe:2.3:o:wago:750-8214_firmware:*:*:*:*:*:*:*:*
wago 750-8216_firmware < fw20 cpe:2.3:o:wago:750-8216_firmware:*:*:*:*:*:*:*:*
wago 750-8217_firmware < fw20 cpe:2.3:o:wago:750-8217_firmware:*:*:*:*:*:*:*:*
codesys plcwinnt < 2.4.7.56 cpe:2.3:a:codesys:plcwinnt:*:*:*:*:*:*:*:*
codesys runtime_toolkit < 2.4.7.56 cpe:2.3:a:codesys:runtime_toolkit:*:*:*:*:*:*:x86:*

References for CVE-2021-34593

cvelogic Threat Intelligence