{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-12259", "assignerOrgId": "c09c270a-b464-47c1-9133-acb35b22c19a", "state": "PUBLISHED", "assignerShortName": "@huntr_ai", "dateReserved": "2026-06-15T09:55:01.162Z", "datePublished": "2026-08-03T07:09:35.262Z", "dateUpdated": "2026-08-03T07:09:35.262Z"}, "containers": {"cna": {"title": "Improper Input Validation in nltk/nltk", "providerMetadata": {"orgId": "c09c270a-b464-47c1-9133-acb35b22c19a", "shortName": "@huntr_ai", "dateUpdated": "2026-08-03T07:09:35.262Z"}, "descriptions": [{"lang": "en", "value": "In nltk version 3.9.4, the `nltk.downloader.Downloader._download_package()` function writes downloaded package bytes to disk and may extract them before enforcing SHA-256 or MD5 checksum validation. This allows an attacker to tamper with the package response body for `info.url` through a compromised mirror, malicious proxy, or other source-substitution condition, leading to the installation of attacker-controlled package bytes. The vulnerability can result in malicious corpus or model content being trusted by downstream users or applications."}], "affected": [{"vendor": "nltk", "product": "nltk/nltk", "versions": [{"version": "unspecified", "status": "affected", "versionType": "custom", "lessThanOrEqual": "latest"}]}], "references": [{"url": "https://huntr.com/bounties/659ccf6d-12d4-4d4a-84c0-078633c35a5d"}], "metrics": [{"cvssV3_0": {"version": "3.0", "attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N", "baseScore": 5.3, "baseSeverity": "MEDIUM"}}], "problemTypes": [{"descriptions": [{"type": "CWE", "lang": "en", "description": "CWE-494 Download of Code Without Integrity Check", "cweId": "CWE-494"}]}], "source": {"advisory": "659ccf6d-12d4-4d4a-84c0-078633c35a5d", "discovery": "EXTERNAL"}}}}

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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[0,*]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "nltk/nltk", "source": "cna", "vendor": "nltk"}, "product": "nltk/nltk", "vendor": "nltk"}], "created": "2026-08-03T09:30:17.608680+00:00", "updated": "2026-08-03T09:30:17.608701+00:00", "vendors": ["nltk", "nltk$PRODUCT$nltk/nltk"]}