{"id":"CVE-2026-80206","title":"nltk: NLTK: Denial of Service vulnerability in tgrep module (CVE-2026-80206)","summary":"A flaw was found in NLTK, specifically within its tgrep module. This vulnerability, known as Regular Expression Denial of Service (ReDoS), allows a remote attacker to provide specially crafted regular expressions. When processed, these exp…","severity":"medium","cvss":5.9,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","cvssSource":"vendor","cwe":"CWE-1333","vendor":"Red Hat","product":"Red Hat OpenShift AI (RHOAI)","affected":["exploit_intelligence","lightspeed_core","openshift_lightspeed","ansible_automation_platform 2","openshift_ai_rhoai"],"patched":["nltk 3.10.3"],"published":"2026-08-26","updated":"2026-10-15","sourceUpdated":"2026-10-15T11:23:06+00:00","source":"CSAF","sourceUrl":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80206.json","references":[{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80206.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-80206"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2524336"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-80206"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80206"},{"url":"https://github.com/nltk/nltk/security/advisories/GHSA-w3v8-gmh9-3wv7"},{"url":"https://www.vulncheck.com/advisories/nltk-3.10.2-regular-expression-denial-of-service-via-tgrep"},{"url":"https://github.com/nltk/nltk/commit/0072ea2fb8be22e038a36e887b7061bb6b9339d9"},{"url":"https://github.com/nltk/nltk"},{"url":"https://github.com/nltk/nltk/releases/tag/v3.10.3"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3751.yaml"},{"url":"https://github.com/advisories/GHSA-w3v8-gmh9-3wv7"}],"tags":["csaf","vex","red-hat","osv","pip","ghsa"],"epss":0.0044,"epssPercentile":0.38089,"aliases":["GHSA-w3v8-gmh9-3wv7","PYSEC-2026-3751"],"ecosystem":"pip","ingestedAt":"2026-09-02T19:31:25.120Z","slug":"CVE-2026-80206","body":"## Overview\n\nA flaw was found in NLTK, specifically within its tgrep module. This vulnerability, known as Regular Expression Denial of Service (ReDoS), allows a remote attacker to provide specially crafted regular expressions. When processed, these expressions can cause indefinite CPU saturation, leading to a complete denial of service for the Python process utilizing the NLTK library.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Exploit Intelligence, Lightspeed Core, OpenShift Lightspeed, Red Hat Ansible Automation Platform 2, Red Hat OpenShift AI (RHOAI) · no fix planned: Exploit Intelligence, Red Hat Ansible Automation Platform 2, Lightspeed Core, OpenShift Lightspeed, … · updated 2026-10-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80206.json)\n\n**nltk: NLTK: Denial of Service vulnerability in tgrep module** — rated Moderate by Red Hat. Released 2026-08-26, updated 2026-10-15.\n\nAffected:\n\n- Exploit Intelligence\n- Lightspeed Core\n- OpenShift Lightspeed\n- Red Hat Ansible Automation Platform 2\n- Red Hat OpenShift AI (RHOAI)\n\nNo fix planned:\n\n- Exploit Intelligence\n- Red Hat Ansible Automation Platform 2\n- Lightspeed Core\n- OpenShift Lightspeed\n- Red Hat OpenShift AI (RHOAI)\n\n## Remediation\n\nOut of support scope\n\nWorkarounds / mitigations:\n\n- Sanitize or restrict external input passed to NLTK's tgrep compilation functions to prevent execution of untrusted regular expressions, or enforce application-level timeouts using process isolation/multiprocessing wrappers to restrict CPU consumption.\n\n## Package advisory (CVE-2026-80206)\n\nAffected packages:\n\n- `nltk < 3.10.3`\n\nPatched in:\n\n- `nltk 3.10.3`\n\nSource: https://osv.dev/vulnerability/GHSA-w3v8-gmh9-3wv7","depth":"sunlit","depthScore":33,"depthScoreParts":{"impact":32.5,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":222207,"id":"CVE-2026-80206","ts":1792065075600,"field":"cvss","old":null,"new":"5.9"},{"seq":222206,"id":"CVE-2026-80206","ts":1792065075600,"field":"severity","old":"high","new":"medium"},{"seq":8232,"id":"CVE-2026-80206","ts":1788919993788,"field":"severity","old":"none","new":"high"},{"seq":8041,"id":"CVE-2026-80206","ts":1788919280771,"field":"severity","old":"high","new":"none"},{"seq":7850,"id":"CVE-2026-80206","ts":1788916354400,"field":"severity","old":"none","new":"high"},{"seq":7659,"id":"CVE-2026-80206","ts":1788915297472,"field":"severity","old":"high","new":"none"},{"seq":7468,"id":"CVE-2026-80206","ts":1788912713848,"field":"severity","old":"none","new":"high"},{"seq":7277,"id":"CVE-2026-80206","ts":1788911331401,"field":"severity","old":"high","new":"none"},{"seq":7081,"id":"CVE-2026-80206","ts":1788909077086,"field":"severity","old":"none","new":"high"},{"seq":6893,"id":"CVE-2026-80206","ts":1788907391505,"field":"severity","old":"high","new":"none"},{"seq":6695,"id":"CVE-2026-80206","ts":1788905443424,"field":"severity","old":"none","new":"high"},{"seq":6513,"id":"CVE-2026-80206","ts":1788903459728,"field":"severity","old":"high","new":"none"},{"seq":6423,"id":"CVE-2026-80206","ts":1788901915446,"field":"severity","old":"none","new":"high"}]}