{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-78683", "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10", "state": "PUBLISHED", "assignerShortName": "VulnCheck", "dateReserved": "2026-08-25T01:17:12.263Z", "datePublished": "2026-08-25T01:30:39.451Z", "dateUpdated": "2026-08-25T01:30:39.451Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10", "shortName": "VulnCheck", "dateUpdated": "2026-08-25T01:30:39.451Z"}, "datePublic": "2026-08-11T00:00:00.000Z", "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."}], "problemTypes": [{"descriptions": [{"lang": "en", "description": "Deserialization of Untrusted Data", "cweId": "CWE-502", "type": "CWE"}]}], "affected": [{"vendor": "nltk", "product": "nltk", "defaultStatus": "unaffected", "packageURL": "pkg:pypi/nltk", "versions": [{"version": "0", "status": "affected", "versionType": "semver", "lessThan": "3.10.0"}, {"version": "3.10.0", "status": "unaffected", "versionType": "semver"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*", "versionEndExcluding": "3.10.0"}]}]}], "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"}}], "references": [{"url": "https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2", "tags": ["vendor-advisory"], "name": "GitHub Security Advisory (GHSA-rhp5-r9x4-f5g2)"}, {"name": "VulnCheck Advisory: NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization", "tags": ["third-party-advisory"], "url": "https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization"}], "credits": [{"lang": "en", "value": "ekaf", "type": "analyst"}], "x_generator": {"engine": "vulncheck-endgame"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "packageURL": "pkg:pypi/nltk", "product": "nltk", "vendor": "nltk", "versions": [{"lessThan": "3.10.0", "status": "affected", "version": "0", "versionType": "semver"}, {"status": "unaffected", "version": "3.10.0", "versionType": "semver"}]}], "source": "disclosure@vulncheck.com"}], "cveTags": [], "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."}], "id": "CVE-2026-78683", "lastModified": "2026-08-25T02:16:53.033", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.6, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 6.0, "source": "disclosure@vulncheck.com", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 9.4, "baseSeverity": "CRITICAL", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "HIGH", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "HIGH", "userInteraction": "PASSIVE", "valueDensity": "NOT_DEFINED", "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/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", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "disclosure@vulncheck.com", "type": "Secondary"}]}, "published": "2026-08-25T02:16:53.033", "references": [{"source": "disclosure@vulncheck.com", "url": "https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2"}, {"source": "disclosure@vulncheck.com", "url": "https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization"}], "sourceIdentifier": "disclosure@vulncheck.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-502"}], "source": "disclosure@vulncheck.com", "type": "Primary"}]}

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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,3.10.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "3.10.0"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "nltk", "source": "cna", "vendor": "nltk"}, "product": "nltk", "vendor": "nltk"}], "created": "2026-08-25T04:15:04.490148+00:00", "updated": "2026-08-25T05:30:16.863212+00:00", "vendors": ["nltk", "nltk$PRODUCT$nltk"]}