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Vulnerabilities

Vulnerability · CVE-2025-41739

An unauthenticated remote attacker, who beats a race condition, can exploit a flaw in the communication servers of the CODESYS Control runtime system on Linux and QNX to trigger an

Published Dec 1, 2025 · catalog updated Jan 7, 2026 · CODESYS CODESYS Runtime Toolkit

Last checked Nov 4, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2025-41739. EPSS is 0.37%. Act only if a listed version of CODESYS CODESYS Runtime Toolkit is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium5.9
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.37%
Remediation
Version ranges on file
Affected products
vendor CODESYS CODESYS Runtime Toolkit 3.5.21.0 <3.5.21.40

An unauthenticated remote attacker, who beats a race condition, can exploit a flaw in the communication servers of the CODESYS Control runtime system on Linux and QNX to trigger an out-of-bounds read via crafted socket communication, potentially causing a denial of service.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor CODESYS CODESYS Runtime Toolkit 3.5.21.0 <3.5.21.403.5.21.0 <3.5.21.40

How to fix CVE-2025-41739

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-41739. EPSS is 0.37%. Act only if a listed version of CODESYS CODESYS Runtime Toolkit is installed.

Which versions are affected?

Compare what you have installed with CODESYS CODESYS Runtime Toolkit 3.5.21.0 <3.5.21.40 3.5.21.0 <3.5.21.40. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.37%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Dec 1, 2025 · EUVD

    Detected

    An unauthenticated remote attacker, who beats a race condition, can exploit a flaw in the communication servers of the CODESYS Control runtime system on Linux and QNX to trigger an out-of-bounds read via crafted socket communication, potentially causing a denial of service.

  2. Jan 7, 2026 · EUVD

    Updated

    An unauthenticated remote attacker, who beats a race condition, can exploit a flaw in the communication servers of the CODESYS Control runtime system on Linux and QNX to trigger an out-of-bounds read via crafted socket communication, potentially causing a denial of service.

Sources

  • CVE.orgVulnerability recordCVE-2025-41739

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-41739

    30-day exploitation probability 0.37%

    first.org
  • EUVDVulnerability recordEUVD-2025-199976

    An unauthenticated remote attacker, who beats a race condition, can exploit a flaw in the communication servers of the CODESYS Control runtime system on Linux and QNX to trigger an out-of-bounds read via crafted socket communication, potentially causing a denial of service.

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 4, 2026
  • CVE.orgOct 27, 2026
  • EUVDOct 27, 2026