{"schemaVersion":3,"id":"CVE-2026-66393","aliases":["GHSA-rf74-v2fm-23pw","PYSEC-2026-3724","UBUNTU-CVE-2026-66393","DEBIAN-CVE-2026-66393","CGA-2wq4-4h4w-g86g","CGA-49rq-h9f5-8533","CGA-9f47-32c7-832c","CGA-f33r-j373-99qp","CGA-jq3v-5ggj-5wcx","CGA-mq47-pch7-72w7","CGA-p99j-9h8g-rjq9","CGA-w4xf-gqfv-r2qw","CGA-wf23-7c3w-6cqw","CGA-4g6j-jgwm-5g4r","CGA-87cq-94q6-mwx5","CGA-9358-xvqq-5x47","CGA-ccxw-fccc-cfh8","CGA-cr46-68ch-mxrx","CGA-mmwm-5cq2-v6x7","CGA-mqm6-q5qv-m74j","CGA-w85q-9x3m-xcmf","CGA-w8p9-93gg-cq2q"],"status":"published","duplicateOf":null,"title":null,"description":"NLTK versions before 3.9.4 contain an unbounded recursion vulnerability in JSONTaggedDecoder.decode_obj() that allows attackers to cause denial of service by supplying deeply nested JSON structures. Attackers can craft JSON payloads exceeding the recursion limit to trigger an unhandled RecursionError that crashes the Python process.","dates":{"published":"2026-08-22T14:12:42.072Z","modified":"2026-08-26T17:55:08.015Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":8.7,"severity":"high","version":"4.0","versionLabel":"v4.0","source":"CVE.org","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"4.0","versionLabel":"v4.0","source":"CVE.org","score":8.7,"severity":"high","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":7.5,"severity":"high","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","exploitability":null,"impact":null,"computed":false},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Pypi","score":8.7,"severity":"high","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","exploitability":null,"impact":null,"computed":true},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Ubuntu","score":8.7,"severity":"high","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Ubuntu","score":7.5,"severity":"high","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","exploitability":10,"impact":6,"computed":true},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Debian","score":8.7,"severity":"high","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","exploitability":null,"impact":null,"computed":true},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Wolfi","score":8.7,"severity":"high","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":true},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Chainguard","score":8.7,"severity":"high","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":true},{"version":"4.0","versionLabel":"v4.0","source":"NVD","score":8.7,"severity":"high","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":7.5,"severity":"high","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00521,"percentile":0.43096,"severity":"low","asOf":"2026-10-20T00:00:00.000Z","change":{"pp":0.15800000000000003,"baselineDate":"2026-09-20T00:00:00.000Z","baselineScore":0.00363},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00521,"percentile":0.43096}],"last30":[{"date":"2026-09-20T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00363,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00521,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00521,"percentile":0.43096}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[{"id":"GITHUB_NLTK_NLTK","name":"Nltk","source":"github","url":"https://github.com/nltk/nltk/security/advisories/GHSA-f8m6-h2c7-8h9x","maturity":"poc","reliabilityScore":0.3,"verified":false,"type":null,"platforms":[],"requiresAuth":null,"exploitdb":null,"metasploit":null}],"exploitCount":1,"weaknesses":[{"id":"CWE-674","name":"Uncontrolled Recursion","description":"The product does not properly control the amount of recursion that takes place,  consuming excessive resources, such as allocated memory or the program stack.","type":"weakness","status":"Draft","abstraction":"Class","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/674.html"}],"affected":[{"vendor":"chainguard","product":"apache-beam-python-3.11-sdk","name":"apache-beam-python-3.11-sdk","label":"apache-beam-python-3.11-sdk","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/apache-beam-python-3.11-sdk","purlType":"apk","versions":[{"text":"< 2.71.0-r8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2.71.0-r8","eol":null,"hubHref":null},{"vendor":"chainguard","product":"apache-beam-python-3.12-sdk","name":"apache-beam-python-3.12-sdk","label":"apache-beam-python-3.12-sdk","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/apache-beam-python-3.12-sdk","purlType":"apk","versions":[{"text":"< 2.71.0-r2","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2.71.0-r2","eol":null,"hubHref":null},{"vendor":"chainguard","product":"apache-beam-python-3.13-sdk","name":"apache-beam-python-3.13-sdk","label":"apache-beam-python-3.13-sdk","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/apache-beam-python-3.13-sdk","purlType":"apk","versions":[{"text":"< 2.71.0-r2","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2.71.0-r2","eol":null,"hubHref":null},{"vendor":"chainguard","product":"kubeflow-pipelines-visualization-server","name":"kubeflow-pipelines-visualization-server","label":"kubeflow-pipelines-visualization-server","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/kubeflow-pipelines-visualization-server","purlType":"apk","versions":[{"text":"< 2.16.0-r3","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2.16.0-r3","eol":null,"hubHref":null},{"vendor":"chainguard","product":"label-studio","name":"label-studio","label":"label-studio","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/label-studio","purlType":"apk","versions":[{"text":"< 1.23.0-r1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.23.0-r1","eol":null,"hubHref":null},{"vendor":"chainguard","product":"nemo","name":"nemo","label":"nemo","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/nemo","purlType":"apk","versions":[{"text":"< 2.7.2-r1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2.7.2-r1","eol":null,"hubHref":null},{"vendor":"chainguard","product":"open-webui","name":"open-webui","label":"open-webui","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/open-webui","purlType":"apk","versions":[{"text":"< 0.8.12-r1","noFixRecorded":false,"fixedIn":null},{"text":"< 0.8.12-r2","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0.8.12-r1 | < 0.8.12-r2","eol":null,"hubHref":null},{"vendor":"chainguard","product":"py3.11-nltk","name":"py3.11-nltk","label":"py3.11-nltk","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/py3.11-nltk","purlType":"apk","versions":[{"text":"< 3.9.4-r0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 3.9.4-r0","eol":null,"hubHref":null},{"vendor":"chainguard","product":"py3.12-nltk","name":"py3.12-nltk","label":"py3.12-nltk","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/py3.12-nltk","purlType":"apk","versions":[{"text":"< 3.9.4-r0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 3.9.4-r0","eol":null,"hubHref":null},{"vendor":"chainguard","product":"py3.13-nltk","name":"py3.13-nltk","label":"py3.13-nltk","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/py3.13-nltk","purlType":"apk","versions":[{"text":"< 3.9.4-r0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 3.9.4-r0","eol":null,"hubHref":null},{"vendor":"wolfi","product":"kubeflow-pipelines-visualization-server","name":"kubeflow-pipelines-visualization-server","label":"kubeflow-pipelines-visualization-server","ecosystem":"Wolfi","cpePart":null,"purl":"pkg:apk/wolfi/kubeflow-pipelines-visualization-server","purlType":"apk","versions":[{"text":"< 2.16.0-r3","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2.16.0-r3","eol":null,"hubHref":null},{"vendor":"wolfi","product":"open-webui","name":"open-webui","label":"open-webui","ecosystem":"Wolfi","cpePart":null,"purl":"pkg:apk/wolfi/open-webui","purlType":"apk","versions":[{"text":"< 0.8.12-r1","noFixRecorded":false,"fixedIn":null},{"text":"< 0.8.12-r2","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0.8.12-r1 | < 0.8.12-r2","eol":null,"hubHref":null},{"vendor":"wolfi","product":"py3.11-nltk","name":"py3.11-nltk","label":"py3.11-nltk","ecosystem":"Wolfi","cpePart":null,"purl":"pkg:apk/wolfi/py3.11-nltk","purlType":"apk","versions":[{"text":"< 3.9.4-r0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 3.9.4-r0","eol":null,"hubHref":null},{"vendor":"wolfi","product":"py3.12-nltk","name":"py3.12-nltk","label":"py3.12-nltk","ecosystem":"Wolfi","cpePart":null,"purl":"pkg:apk/wolfi/py3.12-nltk","purlType":"apk","versions":[{"text":"< 3.9.4-r0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 3.9.4-r0","eol":null,"hubHref":null},{"vendor":"wolfi","product":"py3.13-nltk","name":"py3.13-nltk","label":"py3.13-nltk","ecosystem":"Wolfi","cpePart":null,"purl":"pkg:apk/wolfi/py3.13-nltk","purlType":"apk","versions":[{"text":"< 3.9.4-r0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 3.9.4-r0","eol":null,"hubHref":null},{"vendor":"debian","product":"nltk","name":"nltk","label":"nltk","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/nltk","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null},{"text":"< 3.10.0-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"All versions (No fix recorded) | < 3.10.0-1","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"nltk","name":"nltk","label":"nltk","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/nltk","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"nltk","product":"nltk","name":"nltk","label":"nltk","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 3.9.4","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 3.9.4","eol":null,"hubHref":"/vendor/nltk/nltk"},{"vendor":"PyPI","product":"nltk","name":"nltk","label":"nltk","ecosystem":"PyPI","cpePart":null,"purl":"pkg:pypi/nltk","purlType":"pypi","versions":[{"text":"< 3.9.4","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 3.9.4","eol":null,"hubHref":null}],"affectedCount":19,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/nltk/nltk/security/advisories/GHSA-rf74-v2fm-23pw","label":"github.com/nltk/nltk/security/advisories/GHSA-rf74-v2fm-23pw","hostname":"github.com","tags":["Vendor Advisory","WEB","EVIDENCE","REPORT","Advisory","Exploit","Mitigation"]},{"url":"https://www.vulncheck.com/advisories/nltk-before-denial-of-service-via-jsontaggeddecoder","label":"www.vulncheck.com/advisories/nltk-before-denial-of-service-via-jsontaggeddecoder","hostname":"www.vulncheck.com","tags":["Third Party Advisory","WEB","Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66393","label":"nvd.nist.gov/vuln/detail/CVE-2026-66393","hostname":"nvd.nist.gov","tags":["Advisory"]},{"url":"https://github.com/nltk/nltk/commit/00cdcd392142e6c745e7120c8d50a24127df5fad","label":"github.com/nltk/nltk/commit/00cdcd392142e6c745e7120c8d50a24127df5fad","hostname":"github.com","tags":["WEB"]},{"url":"https://github.com/nltk/nltk","label":"github.com/nltk/nltk","hostname":"github.com","tags":["PACKAGE"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3724.yaml","label":"github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3724.yaml","hostname":"github.com","tags":["WEB"]},{"url":"https://ubuntu.com/security/CVE-2026-66393","label":"ubuntu.com/security/CVE-2026-66393","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-66393","label":"www.cve.org/CVERecord?id=CVE-2026-66393","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-66393","label":"security-tracker.debian.org/tracker/CVE-2026-66393","hostname":"security-tracker.debian.org","tags":["Advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66393.json","label":"github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66393.json","hostname":"github.com","tags":["Advisory"]}],"lineage":{"upstream":["GHSA-CV2G-M8RR-888C"],"downstream":[],"duplicates":[],"related":["CGA-88J4-W33C-HF4F"]},"timeline":[{"kind":"published","date":"2026-08-22T14:12:42.072Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-08-26T17:55:08.015Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":45,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-20T23:48:14.323Z","stale":false,"partial":false}}