{"items":[{"id":"NVI-00013901","kind":"vulnerability","title":"NLTK: Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution","revision":2,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-rhp5-r9x4-f5g2","CVE-2026-78683"],"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-1f79911c18b216788d1c7ab89ade3956"],"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":"EPSS","as_of":"2026-11-02T12:00:30.000Z","value":"0.510%","meaning":"FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.43551. Missing scores are unknown.","source_id":"sr-1f79911c18b216788d1c7ab89ade3956"}],"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-1982237de373e82ae66e40dabf792740","url":"https://github.com/advisories/GHSA-rhp5-r9x4-f5g2","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-rhp5-r9x4-f5g2","publisher":"GitHub Advisory Database","observed_at":"2026-11-02T02:20:31.767Z"},{"id":"sr-1f79911c18b216788d1c7ab89ade3956","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-2026-78683","publisher":"FIRST EPSS","observed_at":"2026-11-02T20:15:58.863Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-1982237de373e82ae66e40dabf792740"],"technology":"nltk","known_exclusions":[],"conditions_summary":"## Summary\n\nThe NLTK library's `TransitionParser.parse()` method deserializes model files using `pickle_load()` with the default `restricted=False` parameter, allowing arbitrary Python code execution when loading a malicious model file. The library provides a `RestrictedUnpickler` class for safe deserialization, but it is never used by production code paths, leaving the vulnerability unpatched.\n\n## Root Cause\n\n**File:** `nltk/parse/transitionparser.py` (lines 542-557)\n\nThe `parse()` method calls `pickle_load(f)` without `restricted=True`, routing through `WarningUnpickler` which inherits from `pickle.Unpickler` and does NOT override `find_class()`. This allows arbitrary class/function resolution during unpickling, enabling RCE via standard pickle gadgets (e.g., `os.system`, `subprocess.Popen`).\n\n**Vulnerability chain in `nltk/picklesec.py`:**\n\n```python\ndef pickle_load(file, *, context=None, restricted=False):\n    if restricted:\n        return RestrictedUnpickler(file).load()  # Safe: blocks all globals\n    return WarningUnpickler(file, context=context).load()  # VULNERABLE PATH\n```\n\n`WarningUnpickler` only emits a warning but does NOT block unsafe class loading — it calls `super()","public_affected_ranges":["<= 3.9.4"]}],"null_published_at":"2026-11-07T14:01:58.731Z","source_updated_at":"2026-09-08T16:41:13.000Z","source_disclosed_at":"2026-09-08T16:41:11.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.","null_first_observed_at":"2026-11-02T02:20:31.767Z"},{"id":"NVI-00013901","kind":"vulnerability","title":"NLTK: Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-rhp5-r9x4-f5g2","CVE-2026-78683"],"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-1982237de373e82ae66e40dabf792740"],"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-1982237de373e82ae66e40dabf792740","url":"https://github.com/advisories/GHSA-rhp5-r9x4-f5g2","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-rhp5-r9x4-f5g2","publisher":"GitHub Advisory Database","observed_at":"2026-11-02T02:20:31.767Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-1982237de373e82ae66e40dabf792740"],"technology":"nltk","known_exclusions":[],"conditions_summary":"## Summary\n\nThe NLTK library's `TransitionParser.parse()` method deserializes model files using `pickle_load()` with the default `restricted=False` parameter, allowing arbitrary Python code execution when loading a malicious model file. The library provides a `RestrictedUnpickler` class for safe deserialization, but it is never used by production code paths, leaving the vulnerability unpatched.\n\n## Root Cause\n\n**File:** `nltk/parse/transitionparser.py` (lines 542-557)\n\nThe `parse()` method calls `pickle_load(f)` without `restricted=True`, routing through `WarningUnpickler` which inherits from `pickle.Unpickler` and does NOT override `find_class()`. This allows arbitrary class/function resolution during unpickling, enabling RCE via standard pickle gadgets (e.g., `os.system`, `subprocess.Popen`).\n\n**Vulnerability chain in `nltk/picklesec.py`:**\n\n```python\ndef pickle_load(file, *, context=None, restricted=False):\n    if restricted:\n        return RestrictedUnpickler(file).load()  # Safe: blocks all globals\n    return WarningUnpickler(file, context=context).load()  # VULNERABLE PATH\n```\n\n`WarningUnpickler` only emits a warning but does NOT block unsafe class loading — it calls `super()","public_affected_ranges":["<= 3.9.4"]}],"null_published_at":"2026-11-02T10:00:37.172Z","source_updated_at":"2026-09-08T16:41:13.000Z","source_disclosed_at":"2026-09-08T16:41:11.000Z","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":"2026-11-02T02:20:31.767Z"}],"next_cursor":null,"snapshot_revision":"42594"}