CVE-2026-63312: nltk Path Traversal

Vulnerability summary

CVE-2026-63312 is a high (CVSS 8.7) Path Traversal vulnerability in nltk. EPSS estimates a 0.65% chance of exploitation in the next 30 days, higher than 50.2% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 22-08-2026
   PublishedVulnerability first disclosed.
2. 24-08-2026
   Last modifiedVulnerability information updated.

Description

NLTK before 3.10.0 contains an arbitrary local file read vulnerability in StreamBackedCorpusView that bypasses pathsec.ENFORCE by calling builtins.open() directly instead of pathsec.open(). Attackers who control the fileid argument can read arbitrary local files regardless of the ENFORCE setting, including sensitive system files and application credentials.

• CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.