{"id":"USN-7365-1","summary":"nltk vulnerabilities","details":"It was discovered that NLTK contained a regex that is susceptible to\ncatastrophic backtracking. An attacker could possibly use this issue to\ncause a denial of service. (CVE-2021-3842, CVE-2021-43854)\n","modified":"2026-06-25T13:32:19.437594541Z","published":"2025-03-24T01:55:52Z","related":["UBUNTU-CVE-2021-3842","UBUNTU-CVE-2021-43854"],"upstream":["CVE-2021-3842","CVE-2021-43854","UBUNTU-CVE-2021-3842","UBUNTU-CVE-2021-43854"],"references":[{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-7365-1"},{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-3842"},{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-43854"}],"affected":[{"package":{"name":"nltk","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/nltk?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0~b9-0ubuntu4.1~esm4"}]}],"versions":["2.0~b9-0ubuntu4","2.0~b9-0ubuntu4.1~esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"python-nltk","binary_version":"2.0~b9-0ubuntu4.1~esm4"}],"availability":"Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-7365-1.json","cves_map":{"ecosystem":"Ubuntu:Pro:14.04:LTS","cves":[{"id":"CVE-2021-3842","severity":[{"score":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","type":"CVSS_V3"},{"score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","type":"CVSS_V3"},{"type":"Ubuntu","score":"medium"}]},{"id":"CVE-2021-43854","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"}]}]}}},{"package":{"name":"nltk","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1-1ubuntu0.1+esm2"}]}],"versions":["3.0.4-1","3.0.5-1","3.1-1","3.1-1ubuntu0.1","3.1-1ubuntu0.1+esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"python-nltk","binary_version":"3.1-1ubuntu0.1+esm2"},{"binary_name":"python3-nltk","binary_version":"3.1-1ubuntu0.1+esm2"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"cves_map":{"ecosystem":"Ubuntu:Pro:16.04:LTS","cves":[{"severity":[{"type":"CVSS_V3","score":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"score":"medium","type":"Ubuntu"}],"id":"CVE-2021-3842"},{"id":"CVE-2021-43854","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"}]}]},"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-7365-1.json"}},{"package":{"name":"nltk","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.2.5-1ubuntu0.1+esm2"}]}],"versions":["3.2.4-1","3.2.5-1","3.2.5-1ubuntu0.1","3.2.5-1ubuntu0.1+esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"python-nltk","binary_version":"3.2.5-1ubuntu0.1+esm2"},{"binary_version":"3.2.5-1ubuntu0.1+esm2","binary_name":"python3-nltk"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-7365-1.json","cves_map":{"ecosystem":"Ubuntu:Pro:18.04:LTS","cves":[{"severity":[{"type":"CVSS_V3","score":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"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"}],"id":"CVE-2021-3842"},{"id":"CVE-2021-43854","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"}]}]}}},{"package":{"name":"nltk","ecosystem":"Ubuntu:Pro:20.04:LTS","purl":"pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Ffocal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.4.5-2ubuntu0.1~esm2"}]}],"versions":["3.4.5-1","3.4.5-2","3.4.5-2ubuntu0.1~esm1"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro","binaries":[{"binary_name":"python3-nltk","binary_version":"3.4.5-2ubuntu0.1~esm2"}]},"database_specific":{"cves_map":{"ecosystem":"Ubuntu:Pro:20.04:LTS","cves":[{"severity":[{"type":"CVSS_V3","score":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","type":"CVSS_V3"},{"type":"Ubuntu","score":"medium"}],"id":"CVE-2021-3842"},{"id":"CVE-2021-43854","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"}]}]},"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-7365-1.json"}}],"schema_version":"1.7.5"}