How severe is CVE-2020-36400?

CVE-2020-36400 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-2020-36400 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-36400?

CVE-2020-36400 affects Zeromq Libzmq. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-36400?

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-2020-36400 published?

CVE-2020-36400 was published on 2021-07-01 and last updated on 2026-06-17.

CVE-2020-36400

CVE-2020-36400 is a critical-severity vulnerability in Zeromq Libzmq 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: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Zeromq Libzmq
Published: 2021-07-01
Last modified: 2026-06-17

Description

ZeroMQ libzmq 4.3.3 has a heap-based buffer overflow in zmq::tcp_read, a different vulnerability than CVE-2021-20235.

Frequently asked questions

What is CVE-2020-36400?: ZeroMQ libzmq 4.3.3 has a heap-based buffer overflow in zmq::tcp_read, a different vulnerability than CVE-2021-20235.
How severe is CVE-2020-36400?: CVE-2020-36400 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-2020-36400 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-36400?: CVE-2020-36400 affects Zeromq Libzmq. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-36400?: 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-2020-36400 published?: CVE-2020-36400 was published on 2021-07-01 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:zeromq:libzmq:4.3.3:*:*:*:*:*:*:*

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