{"id":"CVE-2021-20237","aliases":["DEBIAN-CVE-2021-20237","EUVD-2021-7676","GHSA-4p5v-h92w-6wxw","GHSA-98wx-fq4r-jfm2","JLSEC-2026-517","UBUNTU-CVE-2021-20237","USN-4920-1"],"status":"published","title":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in...","description":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-10","score":0.01694,"percentile":0.77321,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-400","CWE-401"],"published":"2021-05-28T10:42:23Z","modified":"2026-10-24T10:50:40Z","fixes":[{"ecosystem":"Debian:12","package":"zeromq3","fixed_in":["4.3.3-1"],"sources":["osv"]},{"ecosystem":"Debian:13","package":"zeromq3","fixed_in":["4.3.3-1"],"sources":["osv"]},{"ecosystem":"Debian:14","package":"zeromq3","fixed_in":["4.3.3-1"],"sources":["osv"]},{"ecosystem":"Julia","package":"ZeroMQ_jll","fixed_in":["4.3.4+0"],"sources":["osv"]},{"ecosystem":"Ubuntu:Pro:18.04:LTS","package":"zeromq3","fixed_in":["4.2.5-1ubuntu0.2+esm2"],"sources":["osv"]},{"ecosystem":"Ubuntu:Pro:20.04:LTS","package":"zeromq3","fixed_in":["4.3.2-2ubuntu1.20.04.1~esm2"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Debian:12","package":"zeromq3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.3.3-1"}]}]},{"source":"osv","ecosystem":"Debian:13","package":"zeromq3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.3.3-1"}]}]},{"source":"osv","ecosystem":"Debian:14","package":"zeromq3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.3.3-1"}]}]},{"source":"osv","ecosystem":"Julia","package":"ZeroMQ_jll","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.3.4+0"}]}]},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"zeromq3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.2.5-1ubuntu0.2+esm2"}]}],"versions":["4.2.1-4ubuntu1","4.2.2-1ubuntu2","4.2.3-1","4.2.3-1build1","4.2.5-1","4.2.5-1ubuntu0.1","4.2.5-1ubuntu0.2","4.2.5-1ubuntu0.2+esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"zeromq3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.3.2-2ubuntu1.20.04.1~esm2"}]}],"versions":["4.3.2-1","4.3.2-2","4.3.2-2ubuntu1","4.3.2-2ubuntu1.20.04.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:14.04:LTS","package":"zeromq3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.0.4+dfsg-2ubuntu0.1+esm3"}]}],"versions":["3.2.3+dfsg-2","3.2.4+dfsg-1","3.2.4+dfsg-2","3.2.4+dfsg-3","3.2.4+dfsg-4","4.0.3+dfsg-1","4.0.4+dfsg-2","4.0.4+dfsg-2ubuntu0.1","4.0.4+dfsg-2ubuntu0.1+esm1","4.0.4+dfsg-2ubuntu0.1+esm2"],"bundled":5},{"source":"osv","ecosystem":"Ubuntu:Pro:16.04:LTS","package":"zeromq3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.1.4-7ubuntu0.1+esm2"}]}],"versions":["4.0.5+dfsg-3ubuntu1~gcc5.1","4.0.5+dfsg-3ubuntu2","4.1.4-7","4.1.4-7ubuntu0.1","4.1.4-7ubuntu0.1+esm1"],"bundled":5},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"zeromq3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.2.5-1ubuntu0.2+esm2"}]}],"versions":["4.2.1-4ubuntu1","4.2.2-1ubuntu2","4.2.3-1","4.2.3-1build1","4.2.5-1","4.2.5-1ubuntu0.1","4.2.5-1ubuntu0.2","4.2.5-1ubuntu0.2+esm1"],"bundled":5},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"zeromq3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.3.2-2ubuntu1.20.04.1~esm2"}]}],"versions":["4.3.2-1","4.3.2-2","4.3.2-2ubuntu1","4.3.2-2ubuntu1.20.04.1~esm1"],"bundled":5}],"products":[{"vendor":"microsoft","product":"zeromq"},{"vendor":"zeromq","product":"libzmq"}],"references":[{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=1921989","tags":["x_refsource_MISC","x_transferred","Issue Tracking","Third Party Advisory","report","web"]},{"url":"https://github.com/zeromq/libzmq/security/advisories/GHSA-4p5v-h92w-6wxw","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-20237"},{"url":"https://github.com/advisories/GHSA-98wx-fq4r-jfm2"},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-20237","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2021-20237","tags":["report"]},{"url":"https://ubuntu.com/security/notices/USN-4920-1","tags":["advisory"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-20237","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2019-13132","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2020-15166","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2021-20234","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2021-20235","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2021-20237","description":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.","status":"published","published":"2021-05-28T10:42:23Z","modified":"2024-08-03T17:37:22.65Z","cwes":["CWE-400"],"updated_at":"2026-11-02T14:32:55.564736Z"}],"euvd":[{"id":"EUVD-2021-7676","description":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.","status":"published","published":"2021-05-28T10:42:23Z","modified":"2024-08-03T17:37:22Z","updated_at":"2026-11-03T03:25:09.355483Z"}],"ghsa":[{"id":"GHSA-98wx-fq4r-jfm2","title":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in...","description":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.","status":"published","published":"2022-05-24T19:03:38Z","modified":"2023-01-27T05:03:55Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-400","CWE-401"],"updated_at":"2026-11-02T14:42:20.947965Z"}],"nvd":[{"id":"CVE-2021-20237","description":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.","status":"published","published":"2021-05-28T11:15:07.97Z","modified":"2026-06-17T03:33:31.573Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"primary"},{"version":"2.0","score":4.3,"vector":"AV:N/AC:M/Au:N/C:N/I:N/A:P","level":"medium","assessor":"primary"}],"cwes":["CWE-400","CWE-401"],"updated_at":"2026-11-02T14:06:53.987491Z"}],"osv":[{"id":"CVE-2021-20237","description":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.","status":"published","published":"2021-05-28T11:15:07.97Z","modified":"2026-10-24T10:50:40.245597056Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:44:18.004149Z"},{"id":"DEBIAN-CVE-2021-20237","description":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.","status":"published","published":"2021-05-28T11:15:07.97Z","modified":"2026-10-23T18:04:48.810412632Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:45:34.311861Z"},{"id":"JLSEC-2026-517","description":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's `src/xpub.cpp` in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.","status":"published","published":"2026-05-20T04:02:19.667Z","modified":"2026-07-25T18:24:33.658352188Z","cvss":[{"version":"2.0","score":4.3,"vector":"AV:N/AC:M/Au:N/C:N/I:N/A:P","level":"medium"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:47:18.573531Z"},{"id":"UBUNTU-CVE-2021-20237","description":"An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.","status":"published","published":"2021-05-28T11:15:00Z","modified":"2026-04-22T12:45:54.208981Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:54:25.728622Z"},{"id":"USN-4920-1","title":"zeromq3 vulnerabilities","description":"It was discovered that ZeroMQ incorrectly handled certain application\nmetadata. A remote attacker could use this issue to cause ZeroMQ to crash,\nor possibly execute arbitrary code. (CVE-2019-13132)\n\nIt was discovered that ZeroMQ mishandled certain network traffic. An\nunauthenticated attacker could use this vulnerability to cause a denial-of-\nservice and prevent legitimate clients from communicating with ZeroMQ.\n(CVE-2020-15166)\n\nIt was discovered that ZeroMQ did not properly manage memory under certain\ncircumstances. If a user or automated system were tricked into connecting\nto one or multiple compromised servers, a remote attacker could use this\nissue to cause a denial of service. (CVE-2021-20234)\n\nIt was discovered that ZeroMQ incorrectly handled memory when processing\nmessages with arbitrarily large sizes under certain circumstances. A remote\nunauthenticated attacker could use this issue to cause a ZeroMQ server to crash,\nresulting in a denial of service, or possibly execute arbitrary code. This issue\nonly affected Ubuntu 18.04 ESM and Ubuntu 20.04 ESM. (CVE-2021-20235)\n\nIt was discovered that ZeroMQ did not properly manage memory under certain\ncircumstances. A remote unauthenticated attacker could use this issue to\ncause a ZeroMQ server to crash, resulting in a denial of service. This issue\nonly affected Ubuntu 18.04 ESM and Ubuntu 20.04 ESM. (CVE-2021-20237)\n","status":"published","published":"2022-06-15T18:16:23Z","modified":"2026-06-29T13:48:53.719481649Z","updated_at":"2026-11-02T16:58:15.159055Z"}]}}