CVE-2026-12259
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.
Does this matter?
Lower severity and a low EPSS score (0.10%). Track it; it rarely justifies an emergency change on its own.
Description
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 3.0
- 5.3 MEDIUMCVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
- EPSS
- 0.10% probability · 1th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-494
- Source
- security@huntr.dev
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.