CVE-2021-34596 | CODESYS V2 runtime: Access of Uninitialized Pointer may result in denial-of-service

A crafted request may cause a read access to an uninitialized pointer in CODESYS V2 Runtime Toolkit 32 Bit full and PLCWinNT prior to versions V2.4.7.56, resulting in a denial-of-service condition.

Published: 2021-10-26 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-34596 is rated Moderate Risk (45/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.83%). 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-2021-34596

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% 0.83% +0.59%
2 2025-04-27 0.34% 0.24% -0.11%
3 2025-03-30 — 0.34% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-34596

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/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:L)
A normal user session is enough; they don’t have to be admin.
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.
 2.8 3.6 [email protected]
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/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:L)
A normal user session is enough; they don’t have to be admin.
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.
 2.8 3.6 [email protected]
4.0 2.0 MEDIUM
AV:N/AC:L/Au:S/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:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 2.9 [email protected]

Weakness enumeration for CVE-2021-34596

Affected software / configurations for CVE-2021-34596

Vendor Product Version Raw CPE
wago 750-823_firmware < fw10 cpe:2.3:o:wago:750-823_firmware:*:*:*:*:*:*:*:*
wago 750-829_firmware < fw17 cpe:2.3:o:wago:750-829_firmware:*:*:*:*:*:*:*:*
wago 750-831_firmware < fw17 cpe:2.3:o:wago:750-831_firmware:*:*:*:*:*:*:*:*
wago 750-832_firmware < fw10 cpe:2.3:o:wago:750-832_firmware:*:*:*:*:*:*:*:*
wago 750-852_firmware < fw17 cpe:2.3:o:wago:750-852_firmware:*:*:*:*:*:*:*:*
wago 750-862_firmware < fw10 cpe:2.3:o:wago:750-862_firmware:*:*:*:*:*:*:*:*
wago 750-880_firmware < fw17 cpe:2.3:o:wago:750-880_firmware:*:*:*:*:*:*:*:*
wago 750-881_firmware < fw17 cpe:2.3:o:wago:750-881_firmware:*:*:*:*:*:*:*:*
wago 750-882_firmware < fw17 cpe:2.3:o:wago:750-882_firmware:*:*:*:*:*:*:*:*
wago 750-885_firmware < fw17 cpe:2.3:o:wago:750-885_firmware:*:*:*:*:*:*:*:*
wago 750-889_firmware < fw17 cpe:2.3:o:wago:750-889_firmware:*:*:*:*:*:*:*:*
wago 750-890_firmware < fw10 cpe:2.3:o:wago:750-890_firmware:*:*:*:*:*:*:*:*
wago 750-891_firmware < fw10 cpe:2.3:o:wago:750-891_firmware:*:*:*:*:*:*:*:*
wago 750-893_firmware < fw10 cpe:2.3:o:wago:750-893_firmware:*:*:*:*:*:*:*:*
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 codesys < 1.1.9.22 cpe:2.3:a:codesys:codesys:*:*:*:*:*:*:*:*
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-2021-34596

cvelogic Threat Intelligence