CVE-2026-12259
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.
- Score
- CVSS 3.1 6.5 Medium
- Status
- Analyzed - security@huntr.dev
- Published
- 2026-08-03
- Last modified
- 2026-10-23
- Weaknesses
- CWE-494
Affected products
References
- https://huntr.com/bounties/659ccf6d-12d4-4d4a-84c0-078633c35a5d
