CVE-2021-20235
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.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 43.9%, higher than 99% of all known CVEs. Patch or mitigate before the next change window.
Description
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 3.1
- 8.1 HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 43.86% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-120, CWE-787
- Affected
- zeromq/libzmq
- Source
- secalert@redhat.com
EPSS 43.9% since 26 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1921983Issue Tracking, Patch, Third Party Advisory
- https://github.com/zeromq/libzmq/security/advisories/GHSA-fc3w-qxf5-7hp6Patch, Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1921983Issue Tracking, Patch, Third Party Advisory
- https://github.com/zeromq/libzmq/security/advisories/GHSA-fc3w-qxf5-7hp6Patch, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.