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NVD / CVE Program· CNA CERTVDE

CVE-2021-34585: CODESYS V2 web server: crafted requests could trigger a pointer dereference with an invalid address (DoS)

Noroxi assessment

Priority: Monitor (action score 30/100)

  • 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: 0.90% (FIRST EPSS); higher than 59.8% 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 the CODESYS V2 web server prior to V1.1.9.22 crafted web server requests can trigger a parser error. Since the parser result is not checked under all conditions, a pointer dereference with an invalid address can occur. This leads to a denial of service situation.

HighCVSS 7.5 · v3.1—No exploit No fix recorded
Published
Oct 26, 2021
Updated
Jun 16, 2026
EPSS
0.9% · 59th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.9%

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-2021-34585

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
codesyscodesys
wago750-823 firmware
wago750-823
wago750-829 firmware
wago750-829
wago750-831 firmware
wago750-831
wago750-832 firmware
wago750-832
wago750-852 firmware
wago750-852
wago750-862 firmware

and 43 more

Affected versions

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

  • codesys codesysbefore 1.1.9.22
  • 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
  • wago 750-823 firmwarebefore fw10
  • wago 750-829 firmwarebefore fw17
  • wago 750-831 firmwarebefore fw17
  • wago 750-832 firmwarebefore fw10
  • wago 750-852 firmwarebefore fw17
  • wago 750-862 firmwarebefore fw10

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

    • all web servers and later · before V1.1.9.22affected

Same product

codesys: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-34586CODESYS V2 web server: crafted requests could trigger a null pointer dereference (DoS)
    34Monitor
  • CVE-2019-135383S-Smart Software Solutions GmbH CODESYS V3 Library Manager, all versions prior to 3.5.16.0, allows the system to display active library con
    34Monitor
  • CVE-2021-34595CODESYS V2 runtime: out-of-bounds read or write access may result in denial-of-service
    32Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-21868Aug 18, 2021 · An unsafe deserialization vulnerability exists in the ObjectManager.plugin Project.get_MissingTypes() functionality of CODESYS GmbH CODESYS
    32Monitor
  • ← EarlierCVE-2021-21869Aug 25, 2021 · An unsafe deserialization vulnerability exists in the Engine.plugin ProfileInformation ProfileData functionality of CODESYS GmbH CODESYS Dev
    32Monitor
  • Later →CVE-2021-34596Oct 26, 2021 · CODESYS V2 runtime: Access of Uninitialized Pointer may result in denial-of-service
    26Monitor

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-252 · Unchecked Return Value

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

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

All records