CVE-2021-20236 Memory corruption in zeromq

What is CVE-2021-20236?

CVE-2021-20236 is a critical memory corruption vulnerability in Fedoraproject Fedora, published on 28 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

A flaw was found in the ZeroMQ server in versions before 4.3.3. This flaw allows a malicious client to cause a stack buffer overflow on the server by sending crafted topic subscription requests and then unsubscribing. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.

Weakness: CWE-787, CWE-120

Which versions are affected by CVE-2021-20236?

It affects 4 products.

Products include Fedoraproject Fedora, Redhat Ceph Storage, Redhat Enterprise Linux, Zeromq Zeromq.

How do I fix CVE-2021-20236?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2021-20236 being exploited?

There is no known exploitation of CVE-2021-20236 in the wild and no public exploit code.

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• CVE-2021-39226 Grafana Authentication Bypass Exploited Critical 9.8
• CVE-2019-5544 VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow Exploited Critical 9.8
• CVE-2024-4947 Google Chromium V8 Type Confusion Exploited Critical 9.6
• CVE-2024-4671 Google Chromium Visuals Use-After-Free Exploited Critical 9.6

All Fedoraproject Fedora vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2021-20236, GHSA-4j25-p3vq-p264, GHSA-qq65-x72m-9wr8, JLSEC-2026-516, UBUNTU-CVE-2021-20236.