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CVE Record

CVE-2025-14009: Zip Slip Vulnerability in nltk/nltk Leading to Remote Code Execution

A critical vulnerability exists in the NLTK downloader component of nltk/nltk, affecting all versions. The _unzip_iter function in nltk/downloader.py uses zipfile.extractall() without performing path validation or security checks. This allows attackers to craft malicious zip packages that, when downloaded and extracted by NLTK, can execute arbitrary code. The vulnerability arises because NLTK assumes all downloaded packages are trusted and extracts them without validation. If a malicious package contains Python files, such as __init__.py, these files are executed automatically upon import, leading to remote code execution. This issue can result in full system compromise, including file system access, network access, and potential persistence mechanisms.

CriticalCVSS 10Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

NLTK’s downloader may unpack crafted ZIP packages without checking paths. A malicious package could place files where they should not go and later run code when imported. The source bundle rates this critical, but it does not show confirmed active exploitation.

Executive priority

Treat as urgent for environments that use NLTK downloader in production, CI, notebooks, or shared data-science platforms. Prioritize containment of download sources and vendor patch review.

Technical view

The issue is in nltk/downloader.py _unzip_iter using zipfile.extractall() without path validation. This creates a Zip Slip-style arbitrary file write path. The bundle states malicious package contents, including Python files, can lead to code execution after import.

Likely exposure

Python environments using NLTK downloader to fetch and extract NLTK packages are the primary concern. Exposure is higher where downloads are automated, mirrors are untrusted, or NLTK data directories are writable by application users.

Exploitation context

KEV is false, and the provided sources do not confirm active exploitation. The risk comes from accepting or retrieving malicious NLTK package archives and extracting them through the vulnerable downloader path.

Researcher notes

The bundle names all versions but provides unspecified version ranges and limited remediation detail. Analysis should focus on downloader extraction behavior, package trust boundaries, filesystem write targets, and import-path exposure without assuming exploit activity.

Mitigation direction

  • Review NLTK, Red Hat, and distribution advisories for patched package guidance.
  • Avoid downloading NLTK packages from untrusted indexes, mirrors, or user-controlled locations.
  • Restrict write permissions on NLTK data and application import paths.
  • Pin trusted package sources and verify integrity where supported.
  • Monitor vendor advisories because affected version and fix detail is incomplete.

Validation and detection

  • Inventory systems, containers, and notebooks that install or import nltk.
  • Identify workflows that call the NLTK downloader automatically.
  • Confirm NLTK package sources are trusted and integrity-controlled.
  • Check whether NLTK data directories overlap with Python import paths.
  • Review Red Hat CSAF and RHSA entries for product-specific status.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-94: Code execution behavior lookup

Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2025-14009 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
10 (3.0)
Known Exploited
No
Published

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
6Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
10CVSS 3.0CriticalCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H3.96@huntr_ai
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

8.8High
CVSS 3.1 vector shape for CVE-2025-14009Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPnltk: Zip Slip Vulnerability in nltk Leading to Code Execution
other:Red Hat severity ratingcvssV3_1
  • 2026-02-18T19:03:28.564Z: Reported to Red Hat.
  • 2026-02-18T17:45:17.573Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
nltknltk/nltkunspecifiedListed
Weakness

CWE details

CWE-94

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-94 · source CWE mapping

Improper Control of Generation of Code ('Code Injection')

Improper Control of Generation of Code ('Code Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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