How severe is CVE-2026-0846?

CVE-2026-0846 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-0846?

CVE-2026-0846 affects the following packages: nltk (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-0846?

Update nltk to 3.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-0846 is resolved across your whole dependency graph.

How do I detect CVE-2026-0846 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nltk, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-0846 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2026-0846 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-0846 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-0846?

CVE-2026-0846 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 46th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-0846?

CVE-2026-0846 is classified as CWE-36 (CWE-36), Path Traversal (CWE-22). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-0846 published, and has it been updated?

CVE-2026-0846 was published on March 9, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

HIGH severity

CVE-2026-0846 — nltk

HIGHFix: nltk/nltk#3485

CVE-2026-0846 is a high-severity (CVSS 7.5) CWE-36 vulnerability in nltk. A fix is available for nltk — see the affected versions and patch details below.

Arbitrary File Read via Absolute Path Input in nltk.util.filestring()

Also known asGHSA-h8wq-7xc4-p3qxPYSEC-2026-97

Published

Mar 9, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 30, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-0846.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk+0.02%

Lower risk than most CVEs46th percentile — riskier than 46% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐍nltk

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`nltk`	all versions	3.9.3`pip install --upgrade 'nltk==3.9.3'`

Affected Products

1 product · 1 configurations

Application

nltknltk

1 version

3.9.2

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nltk, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nltk to 3.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-0846 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This IMPORTANT vulnerability in NLTK allows arbitrary file reads through the `nltk.util.filestring()` function. Exploitation requires no authentication and is network-accessible when the function is exposed to untrusted input. Impact is high confidentiality loss as sensitive files like credentials and configuration…

Product	Fixed in	Advisory
Red Hat OpenShift AI 2.25	`rhoai/odh-llama-stack-core-rhel9:1775144403`	RHSA-2026:10184
Red Hat OpenShift AI 3.3	`rhoai/odh-pipeline-runtime-pytorch-llmcompressor-cuda-py312-rhel9:1778262893`	RHSA-2026:19712

UbuntuHIGH

USN-8302-1Ubuntu

Frequently Asked Questions

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.

O3 Security · Impact-Aware SCA

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