What is CVE-2026-62385?

CVE-2026-62385 is a high-severity path traversal vulnerability in nltk (pip), affecting versions <= 3.9.4. It is fixed in 3.10.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.

How severe is CVE-2026-62385?

CVE-2026-62385 has a CVSS score of 5.9 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of nltk are affected by CVE-2026-62385?

nltk (pip) versions <= 3.9.4 is affected.

Is there a fix for CVE-2026-62385?

Yes. CVE-2026-62385 is fixed in 3.10.0. Upgrade to this version or later.

Is CVE-2026-62385 exploitable, and should I be worried?

Whether CVE-2026-62385 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2026-62385 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

How do I fix CVE-2026-62385?

Upgrade nltk to 3.10.0 or later.

CVE-2026-62385 in nltk

Q: How severe is CVE-2026-62385?

CVE-2026-62385 has a CVSS score of 5.9 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of nltk are affected by CVE-2026-62385?

nltk (pip) versions <= 3.9.4 is affected.

Q: Is there a fix for CVE-2026-62385?

Yes. CVE-2026-62385 is fixed in 3.10.0. Upgrade to this version or later.

Q: Is CVE-2026-62385 exploitable, and should I be worried?

Whether CVE-2026-62385 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2026-62385 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2026-62385?

Upgrade nltk to 3.10.0 or later.

Summary

NLTK: Stable FrameNet and NKJP readers parse outside-root XML

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

Resources

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.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-62385 has a CVSS score of 5.9 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.10.0); upgrading removes the vulnerable code path.

Affected versions

nltk (<= 3.9.4)

Security releases

nltk → 3.10.0 (pip)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

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.

Frequently Asked Questions

What is CVE-2026-62385? CVE-2026-62385 is a high-severity path traversal vulnerability in nltk (pip), affecting versions <= 3.9.4. It is fixed in 3.10.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
How severe is CVE-2026-62385? CVE-2026-62385 has a CVSS score of 5.9 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of nltk are affected by CVE-2026-62385? nltk (pip) versions <= 3.9.4 is affected.
Is there a fix for CVE-2026-62385? Yes. CVE-2026-62385 is fixed in 3.10.0. Upgrade to this version or later.
Is CVE-2026-62385 exploitable, and should I be worried? Whether CVE-2026-62385 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2026-62385 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2026-62385? Upgrade nltk to 3.10.0 or later.