What’s Vulnerable › Vulnerabilities

CVE-2026-63312: NLTK StreamBackedCorpusView Bypasses pathsec.ENFORCE Arbitrary File Read

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-08-22 · updated 2026-10-14
• Weakness: CWE-22

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.

Affected products

• nltk: before 3.10.0 — fixed in 3.10.0

How to fix

Upgrade to a fixed version: nltk 3.10.0. Check the vendor advisory for mitigations.

References

• https://github.com/nltk/nltk/security/advisories/GHSA-x5ph-mj9p-rfr8
• https://www.vulncheck.com/advisories/nltk-streambackedcorpusview-bypasses-pathsec-enforce-arbitrary-file-read
• https://github.com/nltk/nltk/security/advisories/GHSA-x5ph-mj9p-rfr8

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