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NVD / CVE Program· CNA CERTVDE

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

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 2.6% (FIRST EPSS); higher than 85.8% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.5 · v3.1—No exploit No fix recorded
Published
Oct 26, 2021
Updated
Jun 16, 2026
EPSS
2.6% · 85th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 2.6%

CNA vs NVD score

NVD
—
CNA · CERTVDE
7.5
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-34593

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
codesysplcwinnt
codesysruntime toolkit
wago750-8202 firmware
wago750-8202
wago750-8203 firmware
wago750-8203
wago750-8204 firmware
wago750-8204
wago750-8206 firmware
wago750-8206
wago750-8207 firmware
wago750-8207

and 16 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • codesys plcwinntbefore 2.4.7.56
  • codesys runtime toolkitbefore 2.4.7.56
  • wago 750-8202 firmwarebefore fw20
  • wago 750-8203 firmwarebefore fw20
  • wago 750-8204 firmwarebefore fw20
  • wago 750-8206 firmwarebefore fw20
  • wago 750-8207 firmwarebefore fw20
  • wago 750-8208 firmwarebefore fw20
  • wago 750-8210 firmwarebefore fw20
  • wago 750-8211 firmwarebefore fw20
  • wago 750-8212 firmwarebefore fw20
  • wago 750-8213 firmwarebefore fw20
  • wago 750-8214 firmwarebefore fw20
  • wago 750-8216 firmwarebefore fw20
  • wago 750-8217 firmwarebefore fw20

Versions reported by the vendor

Affected version ranges reported by the assigning authority (CERTVDE). Independent of NVD's CPE analysis and usually ahead of it.

  • CODESYS CODESYS V2

    • Runtime Toolkit 32 bit full and later · before V2.4.7.56affected
    • PLCWinNT and later · before V2.4.7.56affected

Same product

codesys: all records

Other highest-scoring records for the same primary product.

  • CVE-2022-31806Insecure default settings in CODESYS Runtime Toolkit 32 bit full and CODESYS PLCWinNT
    39Monitor
  • CVE-2022-32143CODESYS runtime system prone to directory acces
    35Monitor
  • CVE-2022-32138CODESYS runtime system prone to denial of service due to Unexpected Sign Extension
    35Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-30186May 25, 2021 · CODESYS V2 runtime system SP before 2.4.7.55 has a Heap-based Buffer Overflow.
    32Monitor
  • ← EarlierCVE-2021-30195May 25, 2021 · CODESYS V2 runtime system before 2.4.7.55 has Improper Input Validation.
    32Monitor
  • Later →CVE-2022-1965Jun 24, 2022 · CODESYS runtime system prone to file deletion due to improper error handling
    32Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-755 · Improper Handling of Exceptional Conditions

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records