CVE-2026-12259Improper Input Validation in nltk/nltk
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 5.3 MEDIUM (v3.0, CNA)CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
- Weakness (CWE)
- CWE-494
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- @huntr_ai
- NVD analysis
- Analyzed
- Record last updated
- Aug 3, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
nltk nltk/nltk nltk:nltk (from the name) | from unspecified through latest | CNA record |
nltk nltk nltk:nltk | 3.9.4 | NVD |
References
- https://huntr.com/bounties/659ccf6d-12d4-4d4a-84c0-078633c35a5dpermissions-required
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.