{"id":"UBUNTU-CVE-2026-80206","details":"NLTK before 3.10.3 contains a regular expression denial of service (ReDoS) vulnerability in the tgrep module. The _tgrep_node_action function compiles user-supplied regular expressions embedded in /regex/ pattern nodes and executes them via re.search against tree node labels without any validation or timeout. An attacker who controls the tgrep pattern (e.g., via tgrep_positions() or tgrep_compile() exposed to external input) can supply a pattern that triggers catastrophic backtracking, causing indefinite CPU saturation that blocks the Python process.","modified":"2026-09-02T19:36:34.390575087Z","published":"2026-08-26T11:16:00Z","upstream":["CVE-2026-80206"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-80206"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-80206"},{"type":"REPORT","url":"https://github.com/nltk/nltk/security/advisories/GHSA-w3v8-gmh9-3wv7"}],"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"}]}],"versions":["2.0~b9-0ubuntu4","2.0~b9-0ubuntu4.1~esm2","2.0~b9-0ubuntu4.1~esm4","2.0~b9-0ubuntu4.1~esm5","2.0~b9-0ubuntu4.1~esm6"],"ecosystem_specific":{"binaries":[{"binary_name":"python-nltk","binary_version":"2.0~b9-0ubuntu4.1~esm6"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-80206.json"}},{"package":{"name":"nltk","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps-legacy%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.4-1","3.0.5-1","3.1-1","3.1-1ubuntu0.1","3.1-1ubuntu0.1+esm1","3.1-1ubuntu0.1+esm2","3.1-1ubuntu0.1+esm3","3.1-1ubuntu0.1+esm4"],"ecosystem_specific":{"binaries":[{"binary_version":"3.1-1ubuntu0.1+esm4","binary_name":"python-nltk"},{"binary_version":"3.1-1ubuntu0.1+esm4","binary_name":"python3-nltk"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-80206.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"}]}],"versions":["3.2.4-1","3.2.5-1","3.2.5-1ubuntu0.1","3.2.5-1ubuntu0.1+esm1","3.2.5-1ubuntu0.1+esm2","3.2.5-1ubuntu0.1+esm3","3.2.5-1ubuntu0.1+esm4"],"ecosystem_specific":{"binaries":[{"binary_version":"3.2.5-1ubuntu0.1+esm4","binary_name":"python-nltk"},{"binary_name":"python3-nltk","binary_version":"3.2.5-1ubuntu0.1+esm4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-80206.json"}},{"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"}]}],"versions":["3.4.5-1","3.4.5-2","3.4.5-2ubuntu0.1~esm1","3.4.5-2ubuntu0.1~esm2","3.4.5-2ubuntu0.1~esm3","3.4.5-2ubuntu0.1~esm4"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-nltk","binary_version":"3.4.5-2ubuntu0.1~esm4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-80206.json"}},{"package":{"name":"nltk","ecosystem":"Ubuntu:Pro:22.04:LTS","purl":"pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Fjammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.5-1","3.6.5-1","3.6.7-1","3.7-1","3.7-1ubuntu0.1~esm1","3.7-1ubuntu0.1~esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-nltk","binary_version":"3.7-1ubuntu0.1~esm2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-80206.json"}},{"package":{"name":"nltk","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Fnoble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.8.1-1","3.8.1-1ubuntu0.1~esm1","3.8.1-1ubuntu0.1~esm2"],"ecosystem_specific":{"binaries":[{"binary_version":"3.8.1-1ubuntu0.1~esm2","binary_name":"python3-nltk"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-80206.json"}},{"package":{"name":"nltk","ecosystem":"Ubuntu:Pro:26.04:LTS","purl":"pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Fresolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.9.1-2","3.9.1-2build1","3.9.2-1","3.9.2-1ubuntu0.1~esm1","3.9.2-1ubuntu0.1~esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-nltk","binary_version":"3.9.2-1ubuntu0.1~esm2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-80206.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"},{"type":"Ubuntu","score":"medium"}]}