What is CVE-2021-45936?

CVE-2021-45936 is a medium-severity vulnerability in Wolfssl Wolfmqtt, classified under Out-of-bounds Write. CVSS score: 5.5/10. Published 2022-01-01.

How severe is CVE-2021-45936?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Buffer overflow in Wolfssl Wolfmqtt

CVE-2021-45936

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

Vulnerability class: Buffer Overflow

Published 2022-01-01 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.009 (57.7th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 58th percentile — 57.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

Wolfssl Wolfmqtt — versions 1.9

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

github.com/wolfSSL/wolfMQTT/commit/84d4b53122e0fa0280c7872350b89d5777dabbb2 (Patch, Third Party Advisory)
github.com/google/oss-fuzz-vulns/blob/main/vulns/wolfmqtt/OSV-2021-1348.yaml (Exploit, Third Party Advisory)
bugs.chromium.org/p/oss-fuzz/issues/detail (Exploit, Third Party Advisory, Issue Tracking)

Frequently asked questions

What is CVE-2021-45936?: CVE-2021-45936 is a medium-severity vulnerability in Wolfssl Wolfmqtt, classified under Out-of-bounds Write. CVSS score: 5.5/10. Published 2022-01-01.
How severe is CVE-2021-45936?: Medium severity. CVSS v3 base score is 5.5 out of 10.