CVE-2021-20235
mediumpriority · attend · 47EPSS 0.439 · 99 %ileEURUUSEPSS · scored 2026-10-28
There's a flaw in the zeromq server in versions before 4.3.3 in src/decoder_allocators.hpp. The decoder static allocator could have its sized changed, but the buffer would remain the same as it is a static buffer. A remote, unauthenticated attacker who sends a crafted request to the zeromq server could trigger a buffer overflow WRITE of arbitrary data if CURVE/ZAP authentication is not enabled. The greatest impact of this flaw is to application availability, data integrity, and confidentiality.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.8–8.1
weaknesses
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affected products (12)
Products and version ranges known to be affected.
also known as (4)
Other names and identifiers for this entity.
sources
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references (10)
External citations — patches, advisories, analysis.
- https://bugzilla.redhat.com/show_bug.cgi?id=1921983cnnvd
- https://github.com/zeromq/libzmq/security/advisories/GHSA-fc3w-qxf5-7hp6cnnvd
- https://nvd.nist.gov/vuln/detail/CVE-2021-20235cnnvd
- https://ubuntu.com/security/CVE-2021-20235Patchcnnvd
- https://vigilance.fr/vulnerability/libzmq-buffer-overflow-via-ZMTP-V1-Packets-34822cnnvd
- https://www.auscert.org.au/bulletins/ESB-2021.0865cnnvd
- https://bugzilla.redhat.com/show_bug.cgi?id=1921983enisa_euvd
- https://github.com/zeromq/libzmq/security/advisories/GHSA-fc3w-qxf5-7hp6enisa_euvd
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