How severe is CVE-2026-62385?

No CVSS score has been assigned to CVE-2026-62385 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-62385?

CVE-2026-62385 affects the following packages: nltk (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-62385?

Update nltk to 3.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-62385 is resolved across your whole dependency graph.

How do I detect CVE-2026-62385 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-2026-62385 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-2026-62385 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-62385 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-2026-62385?

CVE-2026-62385 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 34th 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-2026-62385?

CVE-2026-62385 is classified as CWE-73 (CWE-73). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-62385 published, and has it been updated?

CVE-2026-62385 was published on August 22, 2026 and was last updated on September 2, 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

CVE-2026-62385 — nltk

Fix: nltk/nltk#3579

CVE-2026-62385 is a CWE-73 vulnerability in nltk. A fix is available for nltk — see the affected versions and patch details below.

NLTK 3.9.4 Path Traversal via FrameNet and NKJP Readers

Also known asGHSA-568f-pv23-39p4PYSEC-2026-3728

Published

Aug 22, 2026

Updated

Sep 2, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 6, 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.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-62385.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs34th percentile — riskier than 34% of all scored CVEsHighest risk

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

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

Summary

Published nltk==3.9.4 still contains several XML-reader entrypoints that build parser paths from caller-controlled selectors or trusted-looking index state without preserving the corpus-root boundary.

Details

Vulnerability type: Path traversal and trusted-root bypass
Affected component: FramenetCorpusReader.frame_by_name, FramenetCorpusReader.doc, FramenetCorpusReader.lu, NKJPCorpusReader.header
Affected versions: Published 3.9.4 reproduced. Current source v3.10.0-rc2 acted as a negative control and blocked the same payloads.
Patched versions: Patched in version 3.10.0, which includes the path-safety rejections seen in the release candidate.
Root cause: Stable reader paths still construct raw XML filenames from unsafe selectors, poisoned index state, or unsafe file identifiers.

I confirmed four public stable entrypoints return parsed outside-root content: a parent-segment traversal frame name, a poisoned fulltext index filename, a poisoned LU id, and an unsafe NKJP header file identifier. Current source rejects the same payloads with explicit path-safety errors, which shows the bug is real but version-scoped to the published stable package.

PoC

Preconditions

The application exposes FrameNet or NKJP reader APIs while trusting NLTK to keep XML parsing inside a corpus root.

Steps

Create a minimal FrameNet or NKJP corpus root and place attacker-chosen XML files outside that root.
Feed unsafe selectors or poisoned index state into the relevant public stable 3.9.4 APIs.
Observe frame_by_name, doc, lu(...).exemplars, or header return parsed outside-root values.
Run the same payloads against current source and observe explicit path-safety rejections.

Minimal reproducible excerpt

framenet_frame_definition FRAME_LEAK
framenet_doc_text DOC_LEAK
framenet_lu_text LU_LEAK
nkjp_header_title HEADER_LEAK

Impact

Applications that process attacker-influenced FrameNet or NKJP corpus selectors or state can be made to parse XML outside the trusted corpus root through normal public reader responses.

Remediation

Keep these reader paths on the same root-confinement model as CorpusReader.open() and nltk.pathsec. Reject unsafe path components before constructing filenames from frame names, document filenames, LU ids, or NKJP file identifiers.

Resources

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`nltk`	all versions	3.10.0`pip install --upgrade 'nltk==3.10.0'`

Affected Products

1 product · 1 configurations

Application

nltknltk

< 3.10.0

range

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 3.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-62385 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 HatModerate

This path traversal flaw in NLTK's FramenetCorpusReader and NKJPCorpusReader can lead to information disclosure by allowing an attacker to read arbitrary XML files outside the intended corpus root. Successful exploitation requires an application to process specially crafted input through the vulnerable NLTK components.

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Source: Red Hat security advisory for CVE-2026-62385 (CC BY 4.0)

Frequently Asked Questions

### Summary Published `nltk==3.9.4` still contains several XML-reader entrypoints that build parser paths from caller-controlled selectors or trusted-looking index state without preserving the corpus-root boundary. ### Details - **Vulnerability type:** Path traversal and trusted-root bypass - **Affected component:** `FramenetCorpusReader.frame_by_name`, `FramenetCorpusReader.doc`, `FramenetCorpusReader.lu`, `NKJPCorpusReader.header` - **Affected versions:** Published `3.9.4` reproduced. Current source `v3.10.0-rc2` acted as a negative control and blocked the same payloads. - **Patched versi

O3 Security · Impact-Aware SCA

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