CVE-2026-65915: NLTK before 3.10.0 Arbitrary File Read via FileSystemPathPointer
NLTK versions before 3.10.0 contain a logic bug in FileSystemPathPointer.open() where the sandbox validation check compares a normalized path against itself, making the security check permanently inert. Attackers can pass file:// URLs to nltk.data.load() to read arbitrary files accessible to the process user, including credentials and configuration files.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
nltkto a version that resolves this vulnerability.Fixed in 3.10.0 - Compensating control
Prevent untrusted users/attackers from controlling the argument passed to nltk.data.load() (e.g., ensure file paths/URIs used by nltk.data.load() are not attacker-controlled, since file:// URLs can enable arbitrary file reads).
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Deployments using NLTK versions before 3.10.0 are exposed when untrusted input can influence values passed to nltk.data.load(). The impact is limited to files readable by the account running the affected process.
What does an attacker need to exploit the flaw?
An attacker needs the ability to supply a file:// URL to nltk.data.load(). No user interaction is required, but the attacker must be able to influence that load target through the application.
Are confidentiality impacts limited to NLTK data files?
No. A successful exploit can read arbitrary files accessible to the process user, including credential and configuration files; the issue does not provide integrity or availability impact in the supplied assessment.
What should be done if upgrading is not immediately possible?
Do not allow untrusted input to reach nltk.data.load(), particularly file:// URLs. Run affected processes with least-privilege filesystem access so sensitive files are not readable by the process account.