CVE-2021-34595 json
CODESYS V2 runtime: out-of-bounds read or write access may result in denial-of-service
published 2021-10-26 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-21245
- cvss
- 8.1
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.9%
- EPSS 0.9% chance of exploitation in 30 days, percentile 58%
- public exploits
- 0
- none known
Summary
A crafted request with invalid offsets may cause an out-of-bounds read or write access in CODESYS V2 Runtime Toolkit 32 Bit full and PLCWinNT prior to versions V2.4.7.56, resulting in a denial-of-service condition or local memory overwrite.
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 8.1
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 < 2.8.0.138affected: mitigation
-
Festo Automation Suite 2.8.0.138 CODESYS Development System 3.5.21.20fixed
Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf
Exploit prediction
0.85% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 8.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H |
| NVD | 3.1 | 8.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H |
| NVD | 2.0 | 5.5 | AV:N/AC:L/Au:S/C:N/I:P/A:P |
Affected products
- CODESYS CODESYS V2
Classification
References
Sources
- CVE List CVE-2021-34595
- NVD CVE-2021-34595
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.