CVE-2021-20235

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.

• CWE-120
• CWE-787

• 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

Published

Apr 1, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2021-2023Vulnerability in the Oracle Installed Base product of Oracle…4.7
• CVE-2021-20230A flaw was found in stunnel before 5.57, where it improperly…7.5
• CVE-2021-20231A flaw was found in gnutls. A use after free issue in client…9.8
• CVE-2021-20232A flaw was found in gnutls. A use after free issue in client…9.8
• CVE-2021-20233A flaw was found in grub2 in versions prior to 2.06. Setpara…8.2
• CVE-2021-20234An uncontrolled resource consumption (memory leak) flaw was …6.5
• CVE-2021-20236A flaw was found in the ZeroMQ server in versions before 4.3…9.8
• CVE-2021-20237An uncontrolled resource consumption (memory leak) flaw was …7.5
• CVE-2021-20238It was found in OpenShift Container Platform 4 that ignition…3.7
• CVE-2021-20239A flaw was found in the Linux kernel in versions before 5.4.…3.3
• CVE-2021-2024Vulnerability in the MySQL Server product of Oracle MySQL (c…6.5
• CVE-2021-20240A flaw was found in gdk-pixbuf in versions before 2.42.0. An…8.8