{"id":"UBUNTU-CVE-2021-42717","details":"ModSecurity 3.x through 3.0.5 mishandles excessively nested JSON objects. Crafted JSON objects with nesting tens-of-thousands deep could result in the web server being unable to service legitimate requests. Even a moderately large (e.g., 300KB) HTTP request can occupy one of the limited NGINX worker processes for minutes and consume almost all of the available CPU on the machine. Modsecurity 2 is similarly vulnerable: the affected versions include 2.8.0 through 2.9.4.","modified":"2026-05-20T16:05:16.521044731Z","published":"2021-12-07T22:15:00Z","related":["USN-6370-1"],"upstream":["CVE-2021-42717"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-42717"},{"type":"REPORT","url":"https://github.com/SpiderLabs/ModSecurity/issues/2647"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-6370-1"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2021-42717"}],"affected":[{"package":{"name":"modsecurity-apache","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/modsecurity-apache?arch=source&distro=esm-apps%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.9.0-1ubuntu0.1~esm1"}]}],"versions":["2.9.0-1"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro","binaries":[{"binary_version":"2.9.0-1ubuntu0.1~esm1","binary_name":"libapache2-mod-security2"},{"binary_name":"libapache2-modsecurity","binary_version":"2.9.0-1ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"}},{"package":{"name":"modsecurity-apache","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/modsecurity-apache?arch=source&distro=esm-apps%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.9.2-1ubuntu0.1~esm1"}]}],"versions":["2.9.1-3","2.9.2-1"],"ecosystem_specific":{"binaries":[{"binary_name":"libapache2-mod-security2","binary_version":"2.9.2-1ubuntu0.1~esm1"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"}},{"package":{"name":"modsecurity-apache","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/modsecurity-apache?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.9.3-1ubuntu0.1"}]}],"versions":["2.9.3-1"],"ecosystem_specific":{"binaries":[{"binary_name":"libapache2-mod-security2","binary_version":"2.9.3-1ubuntu0.1"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"}},{"package":{"name":"modsecurity","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/modsecurity?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.3-1","3.0.4-1","3.0.4-1build1"],"ecosystem_specific":{"binaries":[{"binary_name":"libmodsecurity3","binary_version":"3.0.4-1build1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"}},{"package":{"name":"modsecurity","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/modsecurity?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.4-2","3.0.6-1"],"ecosystem_specific":{"binaries":[{"binary_name":"libmodsecurity3","binary_version":"3.0.6-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"}},{"package":{"name":"modsecurity","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/modsecurity?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.10-1","3.0.11-1","3.0.12-1","3.0.12-1.1build1","3.0.12-1.1build2"],"ecosystem_specific":{"binaries":[{"binary_name":"libmodsecurity3t64","binary_version":"3.0.12-1.1build2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"}},{"package":{"name":"modsecurity","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/modsecurity?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.13-1","3.0.14-1","3.0.14-1build1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.0.14-1build1","binary_name":"libmodsecurity3t64"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"}},{"package":{"name":"modsecurity","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/modsecurity?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.14-1build1","3.0.14-1build2"],"ecosystem_specific":{"binaries":[{"binary_version":"3.0.14-1build2","binary_name":"libmodsecurity3t64"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"medium"}]}