Affected: Homebrew: acronym

NLTK's package downloader in nltk/downloader.py does not verify file integrity after download and before extraction.

The download flow at lines 789-825: 1. File is downloaded to a temp path via HTTP 2. os.replace(tmp_filepath, filepath) moves it to the final location (line 799) 3. Extraction begins via _unzip_iter() (line 825)

Between steps 2 and 3, there is no SHA-256 verification. The checksum logic exists in _pkg_status() (lines 982-1015) but it is only used BEFORE download as a status check ("is this package already installed and up-to-date?"). It is never called after download to verify the file that was actually received.

Attack vectors: 1. MITM during HTTP download (NLTK downloads from http:// by default on some mirrors) 2. Race condition on shared filesystems (attacker replaces file between os.replace and _unzip_iter) 3. DNS poisoning redirecting to attacker-controlled server

PoC: ```python import nltk import unittest.mock import zipfile import io import os

# Create a malicious zip that will be "downloaded" malicious_zip = io.BytesIO() with zipfile.ZipFile(malicious_zip, 'w') as zf: zf.writestr('punkt_tab/tokenizers/punkt_tab/english.pickle', b'MALICIOUS PAYLOAD - attacker controlled content')

# Patch urllib to return our malicious zip with unittest.mock.patch('urllib.request.urlopen') as mock_urlopen: mock_response = unittest.mock.MagicMock() mock_response.read.return_value = malicious_zip.getvalue() mock_response.headers = {'C…

Rejected reason: This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.

Withdrawn by the publisher.

Affected: PyPI: nltk

## Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-5wp5-5229-5g6q. This link is maintained to preserve external references.

## Original Description NLTK before 3.9.3 fails to verify file integrity after downloading packages and before extraction in the downloader module. Attackers can perform man-in-the-middle attacks or DNS poisoning to inject malicious package contents that are extracted without validation.

Affected: PyPI: nltk

NLTK before 3.9.3 fails to verify file integrity after downloading packages and before extraction in the downloader module. Attackers can perform man-in-the-middle attacks or DNS poisoning to inject malicious package contents that are extracted without validation.

golang: net/url: Memory exhaustion in query parameter parsing in net/url urllib3: urllib3 Streaming API improperly handles highly compressed data nltk: NLTK: Arbitrary Code Execution via Eval Injection in Collocations Module undici: Undici: HTTP Request Smuggling and Denial of Service due to duplicate Content-Length headers undici: undici: Denial of Service via unbounded memory consumption during WebSocket permessage-deflate decompression undici: undici: Denial of Service via crafted WebSocket frame with large length undici: Undici: Denial of Service via invalid WebSocket permessage-deflate extension parameter jupyter-server: jupyter-server: Sensitive data exposure via path traversal vulnerability fast-uri: fast-uri: Path traversal vulnerability allows bypass of security policies undici: undici: Information disclosure and data integrity issues due to incorrect Socks5ProxyAgent connection routing undici: undici: Man-in-the-Middle attack via ignored TLS options with SOCKS5 proxy keras: Keras: Arbitrary file write via path traversal in archive extraction utilities sqlite: SQLite: Arbitrary code execution via crafted FTS5 full-text search data sqlite: SQLite: Arbitrary code execution and crash via heap-based buffer overflow in FTS5 undici: undici: Denial of Service due to unbounded memory growth via WebSocket frames brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity guardrails-detectors: guardrails-detectors: Unauthenticated Regular-Expression…

Withdrawn by the publisher.

Affected: Ubuntu:Pro:14.04:LTS: nltk, Ubuntu:Pro:16.04:LTS: nltk, Ubuntu:Pro:18.04:LTS: nltk, Ubuntu:Pro:20.04:LTS: nltk, Ubuntu:Pro:22.04:LTS: nltk, Ubuntu:Pro:24.04:LTS: nltk, Ubuntu:Pro:26.04:LTS: nltk

NLTK before 3.9.3 fails to verify file integrity after downloading packages and before extraction in the downloader module. Attackers can perform man-in-the-middle attacks or DNS poisoning to inject malicious package contents that are extracted without validation.