How severe is CVE-2021-34432?

CVE-2021-34432 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-34432 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34432?

CVE-2021-34432 affects Eclipse Mosquitto. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-34432?

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

When was CVE-2021-34432 published?

CVE-2021-34432 was published on 2021-07-27 and last updated on 2026-07-02.

CVE-2021-34432

CVE-2021-34432 is a high-severity vulnerability in Eclipse Mosquitto with a CVSS 3.x base score of 7.5. 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-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (66th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Eclipse Mosquitto
Published: 2021-07-27
Last modified: 2026-07-02

Description

In Eclipse Mosquitto versions 2.0.7 and earlier, the server will crash if the client tries to send a PUBLISH packet with topic length = 0.

Frequently asked questions

What is CVE-2021-34432?: In Eclipse Mosquitto versions 2.0.7 and earlier, the server will crash if the client tries to send a PUBLISH packet with topic length = 0.
How severe is CVE-2021-34432?: CVE-2021-34432 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-34432 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34432?: CVE-2021-34432 affects Eclipse Mosquitto. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-34432?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-34432 published?: CVE-2021-34432 was published on 2021-07-27 and last updated on 2026-07-02.

References

https://bugs.eclipse.org/bugs/show_bug.cgi?id=574141

Affected products (1)

cpe:2.3:a:eclipse:mosquitto:*:*:*:*:*:*:*:*

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Threat intelligence

Threat-intel indicators referencing this CVE:

182.95.185.158 (ipv4-addr)
182.95.101.182 (ipv4-addr)
182.76.86.130 (ipv4-addr)
128.185.201.170 (ipv4-addr)
125.19.157.158 (ipv4-addr)
27.123.111.110 (ipv4-addr)
182.95.48.154 (ipv4-addr)
182.95.228.106 (ipv4-addr)