CVE-2021-20235 Memory corruption in zeromq
A remote attacker can trigger a buffer overflow in ZeroMQ via crafted requests if authentication is disabled, potentially leading to code execution or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-20235?
CVE-2021-20235 is a high-severity memory corruption vulnerability in zeromq, published on 1 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2021-20235?
It affects 1 product.
Products include Zeromq Libzmq.
How do I fix CVE-2021-20235?
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-2021-20235 being exploited?
There is no known exploitation of CVE-2021-20235 in the wild and no public exploit code.
Other vulnerabilities in zeromq
Sources
Also known as DEBIAN-CVE-2021-20235, GHSA-fc3w-qxf5-7hp6, GHSA-hrfc-mjc4-cv8f, JLSEC-2026-515, UBUNTU-CVE-2021-20235.