{"id":"CVE-2026-78683","summary":"NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization","details":"NLTK before 3.10.0 (affected versions \u003c=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_load() with the default restricted=False, routing deserialization through WarningUnpickler, which does not override find_class() and therefore permits arbitrary class resolution. When an application loads an attacker-crafted model file, embedded pickle gadget chains execute arbitrary Python code with the privileges of the user running the application. NLTK provides a RestrictedUnpickler for safe deserialization, but it is not used by production code paths. Fixed in 3.10.0.","aliases":["GHSA-rhp5-r9x4-f5g2","PYSEC-2026-3734"],"modified":"2026-09-02T03:47:20.804610312Z","published":"2026-08-25T01:30:39.451Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-502"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/78xxx/CVE-2026-78683.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/78xxx/CVE-2026-78683.json"},{"type":"ADVISORY","url":"https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-78683"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/nltk/nltk","events":[{"introduced":"0"},{"fixed":"bd49f9011d7dc8c6a36b3c4ae71f04060c9b3fb9"}],"database_specific":{"cpe":"cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"0"},{"fixed":"3.10.0"}],"source":["AFFECTED_FIELD","CPE_RANGE"]}}],"versions":["v3.10.0-rc1","3.9.4","3.9.3","v3.9.2","3.9.2","3.9.1","3.9","3.8.2","3.8.1","3.8","3.7","3.6.7","3.6.6","3.6.5","3.6.2","3.6.1","3.6","3.5","3.5b1","3.4.4","3.4.3","3.4.1","3.4","3.3","3.2.5","3.2.4","3.2.3","3.2.2","3.2.1","3.2","3.1","3.0.5","3.0.4","3.0.3","3.0.2","3.0.0b1","3.0a4","2.0.1rc4","2.0.1rc3","2.0.1rc2","2.0.1rc1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-78683.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H"}]}