CVE-2026-12259

{"id": "CVE-2026-12259", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-12259", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-08-03T14:55:19.698104Z"}}], "cvssMetricV30": [{"type": "Secondary", "source": "security@huntr.dev", "cvssData": {"scope": "UNCHANGED", "version": "3.0", "baseScore": 5.3, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N", "integrityImpact": "HIGH", "userInteraction": "REQUIRED", "attackComplexity": "HIGH", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 1.6}]}, "affected": [{"source": "security@huntr.dev", "affectedData": [{"vendor": "nltk", "product": "nltk/nltk", "versions": [{"status": "affected", "version": "unspecified", "versionType": "custom", "lessThanOrEqual": "latest"}]}]}], "published": "2026-08-03T08:17:17.880", "references": [{"url": "https://huntr.com/bounties/659ccf6d-12d4-4d4a-84c0-078633c35a5d", "source": "security@huntr.dev"}], "vulnStatus": "Undergoing Analysis", "weaknesses": [{"type": "Secondary", "source": "security@huntr.dev", "description": [{"lang": "en", "value": "CWE-494"}]}], "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."}], "lastModified": "2026-08-31T19:35:51.890", "sourceIdentifier": "security@huntr.dev"}