CVE catalog
CVE-2021-20235
zeromq3: CVE-2021-20235
- Severity
- High · CVSS 8.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 43.86% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | zeromq3 | sid | 4.3.5-1 | fixed |
| Debian | zeromq3 | forky | 4.3.5-1 | fixed |
| Debian | zeromq3 | trixie | 4.3.5-1 | fixed |
| Debian | zeromq3 | bookworm | 4.3.4-6 | fixed |
| Ubuntu | zeromq3 | pro | 4.3.2-1 | vulnerable |
| Ubuntu | zeromq3 | pro | 4.3.2-2 | vulnerable |
| Ubuntu | zeromq3 | pro | 4.3.2-2ubuntu1 | vulnerable |
| Ubuntu | zeromq3 | pro | 4.3.2-2ubuntu1.20.04.1~esm1 | vulnerable |
| Ubuntu | zeromq3 | pro | 4.3.2-2ubuntu1.20.04.1~esm2 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | zeromq3 | source | sid | 4.3.3-1 | not yet assigned | Not reported | Not reported |
| Debian | zeromq3 | source | forky | 4.3.3-1 | not yet assigned | Not reported | Not reported |
| Debian | zeromq3 | source | trixie | 4.3.3-1 | not yet assigned | Not reported | Not reported |
| Debian | zeromq3 | source | bookworm | 4.3.3-1 | not yet assigned | Not reported | Not reported |
| Ubuntu | zeromq3 | deb | pro | 4.3.2-2ubuntu1.20.04.1~esm2 | Not reported | UBUNTU-CVE-2021-20235 | Not reported |
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [libzmq3-dev]Fixed
Source package: [zeromq3]
Details (2)
4.3.4-6· amd64 · bookwormFixed · Fixed:
4.3.3-1dsa · zeromq3 · debian · bookworm; dsa · zeromq3 · debian · 12
4.3.4-6· arm64 · bookwormFixed · Fixed:
4.3.3-1dsa · zeromq3 · debian · bookworm; dsa · zeromq3 · debian · 12
- [libzmq5]Fixed
Source package: [zeromq3]
Details (2)
4.3.4-6· amd64 · bookwormFixed · Fixed:
4.3.3-1dsa · zeromq3 · debian · bookworm; dsa · zeromq3 · debian · 12
4.3.4-6· arm64 · bookwormFixed · Fixed:
4.3.3-1dsa · zeromq3 · debian · bookworm; dsa · zeromq3 · debian · 12
[Debian 13 (Trixie)]
- [libzmq3-dev]Fixed
Source package: [zeromq3]
Details (2)
4.3.5-1+b3· amd64 · trixieFixed · Fixed:
4.3.3-1dsa · zeromq3 · debian · 13
4.3.5-1+b3· arm64 · trixieFixed · Fixed:
4.3.3-1dsa · zeromq3 · debian · 13
- [libzmq5]Fixed
Source package: [zeromq3]
Details (2)
4.3.5-1+b3· amd64 · trixieFixed · Fixed:
4.3.3-1dsa · zeromq3 · debian · 13
4.3.5-1+b3· arm64 · trixieFixed · Fixed:
4.3.3-1dsa · zeromq3 · debian · 13
Observed:
References
- [https://osv.dev/vulnerability/DEBIAN-CVE-2021-20235]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2021-20235]
- [https://security-tracker.debian.org/tracker/CVE-2021-20235]
- [https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-20235.json]
[Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]