CVE-2021-43083: Apache PLC4X 0.9.0 Buffer overflow in PLC4C via crafted server response

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-12-19 · updated 2026-06-17
Weakness: CWE-119

Description

Apache PLC4X - PLC4C (Only the C language implementation was effected) was vulnerable to an unsigned integer underflow flaw inside the tcp transport. Users should update to 0.9.1, which addresses this issue. However, in order to exploit this vulnerability, a user would have to actively connect to a mallicious device which could send a response with invalid content. Currently we consider the probability of this being exploited as quite minimal, however this could change in the future, especially with the industrial networks growing more and more together.

Affected products

Apache Software Foundation Apache PLC4X: before 0.9.1 — fixed in 0.9.1

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache PLC4X 0.9.1. Check the vendor advisory for mitigations.

References

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