NLTK: Untrusted Search Path (CVE-2026-128134)
Published Last modified Sources: CVE.org, EUVD
What is affected, what to do
NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. Prior to 3.10.4, nltk.parse.dependencygraph.dot2img resolves the Graphviz dot executable through PATH but invokes the resulting absolute executable without routing through spawn_trusted, so resolve_trusted_executable ownership and writability validation and safe_env loader environment scrubbing do not run.
Update NLTK to version 3.10.4.
- Affected
- NLTK
lt *..3.10.4
- NLTK
- Fixed in
- NLTK
3.10.4
- NLTK
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Metrics
7.8
XIEM Effective CVSS
Highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
7.8
CVSS v3
Severity High on the scale from 0 to 10.
Source: CVE.org, EUVD
—
EPSS score
No value is available for this vulnerability.
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 69.00 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 7.8 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 7.8
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-426, CWE-427
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. Prior to 3.10.4, nltk.parse.dependencygraph.dot2img resolves the Graphviz dot executable through PATH but invokes the resulting absolute executable without routing through spawn_trusted, so resolve_trusted_executable ownership and writability validation and safe_env loader environment scrubbing do not run. A local low-privileged attacker who can write to a directory on a POSIX victim's PATH can plant or replace dot, and code executes as the victim when dot2img is called directly or DependencyGraph.repr_svg renders a graph. The current-working-directory-only bare-name vector is blocked and is not this vulnerability; this issue is the residual writable absolute PATH element bypass after CVE-2026-78680. This issue is fixed in version 3.10.4.
Source: cvelistv5, NVD (NIST), CVE.org (MITRE), ENISA EUVD
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| nltk | nltk |
|
|
Vendors and products
Weakness classes (CWE)
CWE-426Untrusted Search Path
Base
The product searches for critical resources using an externally-supplied search path that can point to resources that are not under the product's direct control.
Entry at MITRE CWE-426CWE-427Uncontrolled Search Path Element
Base
The product uses a fixed or controlled search path to find resources, but one or more locations in that path can be under the control of unintended actors.
Entry at MITRE CWE-427
References & sources
- github.comnltk/nltk/security/advisories/GHSA-7mxv-7h3q-9324euvd, x_refsource_CONFIRM
- github.comnltk/nltk/pull/3887euvd, x_refsource_MISC
- github.comnltk/nltk/commit/b002a7288c22db86fd6ca2d9526e3f91d6fda797euvd, x_refsource_MISC
- github.comnltk/nltk/releases/tag/v3.10.4euvd, x_refsource_MISC
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
ReceivedGitHub
CVSS V3.1: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness type: CWE-427, CWE-426
Description added or changed
Show 9 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. Prior to 3.10.4, nltk.parse.dependencygraph.dot2img resolves the Graphviz dot executable through PATH but invokes the resulting absolute executable without routing through spawn_trusted, so resolve_trusted_executable ownership and writability validation and safe_env loader environment scrubbing do not run. A local low-privileged attacker who can write to a directory on a POSIX victim's PATH can plant or replace dot, and code executes as the victim when dot2img is called directly or DependencyGraph.repr_svg renders a graph. The current-working-directory-only bare-name vector is blocked and is not this vulnerability; this issue is the residual writable absolute PATH element bypass after CVE-2026-78680. This issue is fixed in version 3.10.4.CVSS added —AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HWeakness type (CWE) added —CWE-427Weakness type (CWE) added —CWE-426Affected versions (publisher) added —New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/128xxx/CVE-2026-128134.json">CVE-2026-128134</a>Reference added —https://github.com/nltk/nltk/commit/b002a7288c22db86fd6ca2d9526e3f91d6fda797Reference added —https://github.com/nltk/nltk/pull/3887Reference added —https://github.com/nltk/nltk/releases/tag/v3.10.4Reference added —https://github.com/nltk/nltk/security/advisories/GHSA-7mxv-7h3q-9324Source identifier: security-advisories@github.com
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-128134"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-128134.svg?lang=en" alt="CVE-2026-128134 – NEOSEC Intel" height="20"></a>