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TI-2021-03530 Aliases CVE-2021-20235GHSA-hrfc-mjc4-cv8f

Buffer overflow in zeromq

Priority MEDIUM 64CWE-120Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Will not fix Red Hat: no fix planned

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-120 and the CVSS impact.

Summary

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.

Why it matters now

EPSS 0.43862 98th percentileScored 2026-11-07
Fix Will not fix Red Hat: no fix planned

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
—zeromqzeromq 4.3.3—No fix listedCNA
  • zeromq Vendor— Affected zeromq 4.3.3 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:zeromq:libzmq:*:*:*:*:*:*:*:*4.2.0 to before 4.3.3Vulnerablezeromq
  • cpe:2.3:a:zeromq:libzmq:*:*:*:*:*:*:*:* Versions 4.2.0 to before 4.3.3 Vulnerable ·zeromq

Remediation

No fixed version listed by the sources yet.

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Ceph Storage 2AffectedNo fix planned: Out of support scope

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-20235
  2. 2026-10-03 Alias added: GHSA-hrfc-mjc4-cv8f

References

Patch 2

  • TI-2019-09836 In ZeroMQ libzmq before 4.0.9, 4.1.x before 4.1.7, and 4.2.x before 4.3.2, a remote… CVSS 3.1CRITICAL 9.8
  • TI-2019-04448 A pointer overflow, with code execution, was discovered in ZeroMQ libzmq (aka 0MQ) 4.2.x… CVSS 3.0HIGH 8.8
  • TI-2020-18651 ZeroMQ libzmq 4.3.3 has a heap-based buffer overflow in zmq::tcp_read, a different vulnerability than CVE-2021-20235. CVSS 3.1CRITICAL 9.8
  • TI-2020-11938 Denial of Service in ZeroMQ CVSS 3.1HIGH 7.5
  • TI-2021-03532 Uncontrolled resource consumption in zeromq CVSS 3.1HIGH 7.5
  • TI-2021-03529 Uncontrolled resource consumption in zeromq CVSS 3.1MEDIUM 6.5

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences