CVE-2020-15166
In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (3.32%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 3.32% probability · 88th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-400
- Affected
- zeromq/libzmq · fedoraproject/fedora · debian/debian linux
- Source
- security-advisories@github.com
EPSS 3.3% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/zeromq/libzmq/pull/3913Patch, Third Party Advisory
- https://github.com/zeromq/libzmq/pull/3973Patch, Third Party Advisory
- https://github.com/zeromq/libzmq/security/advisories/GHSA-25wp-cf8g-938mPatch, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/11/msg00017.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BZ5IMNQXDB52JFBXHFLK4AHVORFELNNG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YFW2ZELCCPS4VLU4OSJOH5YL6KFKTFYW/
- https://security.gentoo.org/glsa/202009-12Third Party Advisory
- https://github.com/zeromq/libzmq/pull/3913Patch, Third Party Advisory
- https://github.com/zeromq/libzmq/pull/3973Patch, Third Party Advisory
- https://github.com/zeromq/libzmq/security/advisories/GHSA-25wp-cf8g-938mPatch, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/11/msg00017.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BZ5IMNQXDB52JFBXHFLK4AHVORFELNNG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YFW2ZELCCPS4VLU4OSJOH5YL6KFKTFYW/
- https://security.gentoo.org/glsa/202009-12Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.