CVE-2021-20237

mediumpriority · track · 31EPSS 0.017 · 77 %ileEURUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

1.69% (77th) EPSS

CVSS 4.3 · medium

Is it mine?

8 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · fstec_bdu · nvd

EPSS · scored 2026-10-28

An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.

cvss

Technical severity, 0–10. One row per scoring source.

7.5

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 4.3–7.5

v2.04.3mediumAV:N/AC:M/Au:N/C:N/I:N/A:Pprimary · NVD / NIST USexploitability 8.6 · impact 2.9

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 3.6

v3.17.5highAV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · FSTEC (BDU) RU

v3.16.9mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-401USprimaryCWE-400USCWE-401US

affected products (8)

Products and version ranges known to be affected.

n/a zeromq≤ zeromq 4.3.3enisa_euvdEU
ООО «РусБИТех-Астра» Astra Linux Special Edition≤ 4.7fstec_bduRU
ООО «РусБИТех-Астра» Astra Linux Special Edition≤ 1.7fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 10fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 12fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 11fstec_bduRU
Сообщество свободного программного обеспечения ZeroMQ4.2.0 → 4.3.3fstec_bduRU
zeromq libzmq4.2.0 → 4.3.3nvdUScpe:2.3:a:zeromq:libzmq:*:*:*:*:*:*:*:*

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu nvd NVD CVE.org MITRE

published 2021-05-28modified 2026-06-17

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+3014 more

references (6)

External citations — patches, advisories, analysis.

scry

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