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Fencer Vulns
high 7.5

CVE-2021-34593 json

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

published 2021-10-26 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-21243

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.7%
EPSS 2.7% chance of exploitation in 30 days, percentile 85%
public exploits
0
none known

Summary

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.

Patch / fix

  • CODESYS CODESYS V2 V2.4.7.56

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

cisa ICSA-26-076-01 updated cvss 7.5

CODESYS in Festo Automation Suite

  • CODESYS Development System 3.0 Festo Automation Suite 2.8.0.137, Festo Automation Suite < 2.8.0.138 CODESYS Development System 3.5.16.10 Festo Automation Suite 2.8.0.137, Festo Automation Suite < 2.8.0.138
    affected: mitigation
  • Festo Automation Suite 2.8.0.138 CODESYS Development System 3.5.21.20
    fixed

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

2.66% chance of exploitation in the next 30 days, higher than 85% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • packetstormsecurity.com http://packetstormsecurity.com/files/164716/CODESYS-2.4.7.0-Denial-Of-Service.html referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/165874/WAGO-750-8xxx-PLC-Denial-Of-Service-User-Enumeration.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • CODESYS CODESYS V2

Classification

Weakness
  • CWE-755 Improper Handling of Exceptional Conditions

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.