How severe is CVE-2021-41036?

CVE-2021-41036 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-41036 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (63rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-41036?

CVE-2021-41036 affects Eclipse Paho Mqtt C/c++ Client. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-41036?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-41036 published?

CVE-2021-41036 was published on 2021-11-03 and last updated on 2026-06-17.

CVE-2021-41036

CVE-2021-41036 is a critical-severity vulnerability in Eclipse Paho Mqtt C/c++ Client with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 1% (63rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Eclipse Paho Mqtt C/c++ Client
Published: 2021-11-03
Last modified: 2026-06-17

Description

In versions prior to 1.1 of the Eclipse Paho MQTT C Client, the client does not check rem_len size in readpacket.

Frequently asked questions

What is CVE-2021-41036?: In versions prior to 1.1 of the Eclipse Paho MQTT C Client, the client does not check rem_len size in readpacket.
How severe is CVE-2021-41036?: CVE-2021-41036 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-41036 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (63rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-41036?: CVE-2021-41036 affects Eclipse Paho Mqtt C/c++ Client. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-41036?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-41036 published?: CVE-2021-41036 was published on 2021-11-03 and last updated on 2026-06-17.

References

https://github.com/eclipse/paho.mqtt.embedded-c/issues/96

Affected products (1)

cpe:2.3:a:eclipse:paho_mqtt_c\/c\+\+_client:*:*:*:*:*:*:*:*

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