Vulnerability · Published Aug 22, 2026 · Assigned by VulnCheck

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

High 7.5

In plain English

A high-severity path traversal in nltk from nltk. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 51% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.7%top 48.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	nltk	no fix listed	DEBIAN-CVE-2026-63312
Debian:13	nltk	no fix listed	DEBIAN-CVE-2026-63312
Debian:14	nltk	3.10.0-1	DEBIAN-CVE-2026-63312
PyPI	nltk	3.10.0	GHSA-x5ph-mj9p-rfr8
PyPI	nltk	3.10.0	PYSEC-2026-3730
Ubuntu:26.10	nltk	no fix listed	UBUNTU-CVE-2026-63312

Affected products (as reported)

Vendor	Product	Versions
nltk	nltk	0 – before 3.10.0

Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

GitHub Security Advisory (GHSA-x5ph-mj9p-rfr8) vendor-advisory
VulnCheck Advisory: NLTK StreamBackedCorpusView Bypasses pathsec.ENFORCE Arbitrary File Read third-party-advisory