CVE-2026-12259: CWE-494 Download of Code Without Integrity Check in nltk nltk/nltk
CVE-2026-12259 is a medium severity vulnerability in nltk version 3.9.4 where the downloader component may write and extract package data before verifying integrity checks such as SHA-256 or MD5. This flaw allows an attacker who can manipulate the package source (e.g., via a compromised mirror or malicious proxy) to substitute malicious package content. As a result, downstream users or applications may trust and use attacker-controlled corpus or model data.
AI Analysis
Technical Summary
In nltk version 3.9.4, the function nltk.downloader.Downloader._download_package() does not enforce checksum validation before writing and extracting downloaded package bytes. This enables an attacker capable of intercepting or substituting the package source URL to deliver tampered package data. The vulnerability is classified under CWE-494 (Download of Code Without Integrity Check) and can lead to installation of malicious corpus or model content that downstream users or applications may trust.
Potential Impact
An attacker who can control or intercept the package download source can cause the installation of malicious package content. This may lead to downstream users or applications trusting and using compromised corpus or model data, potentially impacting data integrity and application behavior. There is no direct confidentiality or availability impact reported.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should avoid downloading packages from untrusted sources or mirrors and consider verifying package integrity manually if possible.
CVE-2026-12259: CWE-494 Download of Code Without Integrity Check in nltk nltk/nltk
Description
CVE-2026-12259 is a medium severity vulnerability in nltk version 3.9.4 where the downloader component may write and extract package data before verifying integrity checks such as SHA-256 or MD5. This flaw allows an attacker who can manipulate the package source (e.g., via a compromised mirror or malicious proxy) to substitute malicious package content. As a result, downstream users or applications may trust and use attacker-controlled corpus or model data.
CVSS v3.0
Score 5.3medium
Affected software
nltk
nltk/nltk
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
In nltk version 3.9.4, the function nltk.downloader.Downloader._download_package() does not enforce checksum validation before writing and extracting downloaded package bytes. This enables an attacker capable of intercepting or substituting the package source URL to deliver tampered package data. The vulnerability is classified under CWE-494 (Download of Code Without Integrity Check) and can lead to installation of malicious corpus or model content that downstream users or applications may trust.
Potential Impact
An attacker who can control or intercept the package download source can cause the installation of malicious package content. This may lead to downstream users or applications trusting and using compromised corpus or model data, potentially impacting data integrity and application behavior. There is no direct confidentiality or availability impact reported.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should avoid downloading packages from untrusted sources or mirrors and consider verifying package integrity manually if possible.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- @huntr_ai
- Date Reserved
- 2026-06-15T09:55:01.162Z
- Cvss Version
- 3.0
- State
- PUBLISHED
Threat ID: 6a704b62bf32cb7a3433eaea
Added to database: 08/03/2026, 08:03:46 UTC
Last enriched: 08/10/2026, 15:17:59 UTC
Last updated: 09/17/2026, 22:01:33 UTC
Views: 52
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