{"id":"CVE-2026-78683","state":"PUBLISHED","title":"NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization","description":"NLTK before 3.10.0 (affected versions <=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.","publishedAt":"2026-08-25T01:30:39.451Z","updatedAt":"2026-08-25T15:19:32.286Z","severity":{"score":9.4,"label":"Critical","version":"4.0","vector":"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","source":"VulnCheck"},"assigner":"VulnCheck","products":["nltk nltk"],"affected":[{"vendor":"nltk","product":"nltk","packageURL":"pkg:pypi/nltk","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"3.10.0","versionType":"semver"},{"version":"3.10.0","status":"unaffected","versionType":"semver"}]}],"references":["https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2","https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization"],"weaknesses":["CWE-502"],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/78xxx/CVE-2026-78683.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-78683","state":"PUBLISHED","datePublished":"2026-08-25T01:30:39.451Z","dateUpdated":"2026-08-25T15:19:32.286Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-08-25T01:17:12.263Z"},"containers":{"cna":{"title":"NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization","descriptions":[{"lang":"en","value":"NLTK before 3.10.0 (affected versions <=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."}],"affected":[{"vendor":"nltk","product":"nltk","packageURL":"pkg:pypi/nltk","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"3.10.0","versionType":"semver"},{"version":"3.10.0","status":"unaffected","versionType":"semver"}]}],"references":[{"url":"https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-rhp5-r9x4-f5g2)"},{"url":"https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization","name":"VulnCheck Advisory: NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","cvssV4_0":{"version":"4.0","vectorString":"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","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"PASSIVE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"HIGH","subIntegrityImpact":"HIGH","subAvailabilityImpact":"HIGH","baseScore":9.4,"baseSeverity":"CRITICAL"}},{"format":"CVSS","cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH","baseScore":9.6,"baseSeverity":"CRITICAL"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-502","lang":"en","description":"Deserialization of Untrusted Data","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-08-25T01:30:39.451Z"},"datePublic":"2026-08-11T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*","versionEndExcluding":"3.10.0"}]}]}],"credits":[{"lang":"en","value":"ekaf","type":"analyst"}],"x_generator":{"engine":"vulncheck-endgame"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-25T15:19:21.370761Z","id":"CVE-2026-78683","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-25T15:19:32.286Z"}}]}}}